Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSTTE SOLID POLYMER ELECTROLYTE MEMBRANES
STATEMENT OF GOVERNMENT RIGHTS
This invention was made with Government support under Contract
No. DE-FC02-97EE50478 awarded by the Department of Energy and
Contract No_ DMI-9760978 with National Science Foundation. The
Government has certain rights in this invention.
FIELD OF THE INVENTION
This invention relates to novel composite solid polymer eiectrolyte
membranes (SPEMs) for use in electrochemical applications. Methods for
producing the composite membranes of the invention are also disclosed.
BACKGROIIND OF THE IN'VENTION
There is a considerable need in both the rnilitary and comsnercial
sectors for quiet, efficient and lightweight power sources that have improved
power density. Military applications include, but are not limited to,
submersibles, surface ships, portable/mobile field generatang units, and low
power units (i_e., battery replacements). For example, the aulitary has a
strong interest in developing low range power sources (a few watts to a,few
lfllowatts) that can function as replacements for batteries. Commercial
applications include transportation (i.e., automotive, bus, truck and
railway), communi.cations, on-site cogeneration and stationary power
generation.
Other interest exists for household applications, such as radios,
camcorders and laptop computers. Additional interests exiist in higher
power sources that can be used in operating clean, efficient vehicles. In
general, there is a need for quiet, efficient, and lightweight power sources
anywhere stationary power generation is needed.
Additiona]ly, the use of gasoline-powered internal combustion
engines has created several environmental, gas-related exhaust problems.
One possible solution to these environmental problems is the use of fuel
cells_ Fuel cells are highly effic.ient electrochemical energy conversion
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devices that direcrlv convert the chemical energy derived from renewable
fuel into electrical energy.
Significant research and development activity has focused on the
development of proton-e.'+cchange membrane fuel cells_ Proton-exchange
; .~
membrane fuel cells have a polymer electrolyte membrane disposed between
a positive electrode (cathode) and a negative electrode (anode). The polymer
electrolyte membrane is composed of a.n ion-exchange polymer (i.e.,
ionomer). Its role is to provide a means for ionic transport and prevent
mixitng of the molecular forms of the fuel and the oxa.dant_
Solid polymer electrolyte fuel cells (SPEFCs) are an ideal source of
quieL, efficient, and lightweight power_ While batteries have reactants
contained within their structure which eventua.lly are used up, fuel cells use
air and hvdrogen. Their fuel efficiency is high. (45 to 50 percent), they do
not
produce noise, operate over a wide power range (10 watts to several hundred
kil.owatts), and are relatively simple to design, masnufacture and operate.
Further, SPEFCs currently have the highest power density of alI fuel cell
types. In addition, SPEFCs do not produce any enviroa=aentallv hazardous
emissions such as NOx an.d SOx (combustion by-products),
The traditional SPEFC contains a solid polymer ion-exchange
membrane that lies betwcen two gas diffusion electrodes, an anode and a
cathode, each commonly containing a metal catalyst supporTed by an
electricallv conductive material. The gas diffusion electrodes are exposed to
the respective reactant gases, the reductant gas and the oxidant gas. An
electrocheraical reaction occurs at each of the two junctions (three phase
boundaries) where one of the electrodes, electrolyte polymer membrane and
reactant gas interface.
During fuel cell operation, hydrogen permeates through the anode
and interacts with the metal catalyst, producing electrons and protons. The
electrons are conducted via an electronic route through the electricaIly
conduccive material and the external circuit to the cathode, while the
protons are siinultaneously transferred via an ionic route through the
polymer electrolyte membrane to the cathode. Oxygen permeates to the
= S
catalyst sites of the cathode, where it gains electrons and reacts with
protons to form water_ Consequently, the products of the SPEFC's reactions
are water and electricity. In the SPEFC, current is conducted
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simultaneously through ionic and electronic routes. Efficiency of the SPEFC
is largeiy dependent on its ability to mi i*nize both ionic and electronic
resistivity to currents.
Ion cxchange membranes play a vital role in SPEFCs. In SPEFCs, the
ion-exchange membrane has two functions: (1) it acts as the electrolyte that
provides ionic cornrnunication between the anode and cathode; and (2) it
serves as a separator for the two reactant gases (e.g_, 02 and H Z). In other
words, the ion-exchange menabrane, wh.ile serving as a good proton transfer
membrane, also must have low permeability for the reactant gases to avoid
cross-over phenomena that reduce performance of the fuel cell_ This is
especially important ia fuel cell applications in which the reactant gases are
under pressure and the fuel cell is operated at elevated temperatures.
Fuel cell reactants are classified as oXidants and reductants on the
basis of their electron acceptor or electron donor characteristics. O~.dants
include pure oxygen, oxygen-containing gases (e_g., air) and halogens (e.g.,
chlorine). Reductants include hydrogen, carbon monoxide, natural gas,
methane, ethane, formaldehyde and methanol.
Optimized proton and water transports of the membrane and proper
water m.anagem.ent are also crucial for efficient fuel ceu application_
Dehydrat.ion of the membrane reduces proton conductivity, and excess
water can lead to swellisa.g of the membranes and flooding of the electrodes.
Both of these conditions lead to poor cell perform.ance.
Despite their potential for many applications, SPEFCs have not yet
been com.mercialized due to unresolved technical problems and high overall
cost_ One major deficiency impacting the connmercialization of the SPEFC is
the inherent limitations of todays leading membrane and electrode
assemblies_ To make the SPEFC com.mercially viable (especially in
automotive applications), the membranes employed must operate at
elevated/high temperatures (> 120 C) so as to provide increased power
density, and lim:it catalyst sensitivity to fuel impurities_ This would also
allow for applications such as on-site cogeneration (high quality waste heat).
Current membranes also allow excessive methanol crossover in liquid feed
direct methanol fuel cells (approximateIy 50 to 200 unA/cm2 @ 0.5V). This
crossover results in poor fuel efficiency as well as Iimited performance
levels.
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Several polymer electrolyte membranes have been developed over the
years for application as solid polymer electrolytes in fuel cells. However,
these membranes have sigiiflcant liznitarions when applied to liquid-feed
direct methanol fuel cells and to hydrogen fuel cells. The znembranes in
today's most advanced SPEFCs do not possess the required combination of
ionic conductivity, mechanical strength, dehydration resistance, and
chemical stability and fuel impermeability (e.g., rnethanoi crossover) to
operate at elevated temperatures.
DuPont developed a series of perfluorinated sulfornic acid membranes
known as Nafion membranes. The Nafion inembxane technology is well
known in the art and is described e_g. in U.S. Patent Nos. 3,282,875 and
4,330,654. Unreinforced Nafong membranes are used almost exclusively
as the ion exchange merr.-brane in present SPEFC applications. This
naembrane is fabricated from tetrafluoroethyiene (TFE), also lffiown as
Tetlon , and a vinvl ether comonomer. The vinyl ether comonomer is
copolymerized with TFE to form, a rnelt-fabricable polysner. Once in the
desired shape, the sulfonyl fluoride group is hydrolyzed into the ionic
sulfonate form.
The fluorocarbon component and the ionic groups are incompatible
(the former is hydrophobic, the latter is hvdrophilic). This causes a phase
separation, which leads to the formation of interconnected hydrated ionic
"clusters". The properties of these clusters determine the electrochemical
c.haracteristics of the polymer, since protons are conducted through the
membrane as they "hop" from one ionic cluster to another. To ensure
proton flow, each acid group needs a minimum amount of water to surround
it and form a cluster. If the acid group concenuation is too low (or
hydration is insufficient) proton transfer will not occur. At higher acid
group concentrations (or increased hydration levels) proton conductivity is
in~proved, but membrane mechanic.al characteristics are sac,ri,ficed.
As the membrane temperature is increased, the swelling forces
(osmotic) become larger than the restraining forces (fluorocarbon chains).
This allows the membrane to assume a more highly swollen state, but may
eventually promote tnerxibrane dehydration_ Peroxide radicals will form
more quickly as the temperature is increased; these radicals can attack and
degrade the membrane. At even higher temperatures (230 C), the
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fluorocarbon phase melts asid permits the ionic phase to "dissolve- (phase
inversion of NafionQ).
There are several mechanisms that limit the performance of Nafionq)
membranes in fuel cell environments at temperatures above 100 C. In fact,
these phenomenon may begin at temperatures above even 80 C. These
mechanisms include membrane dehydration, reduction of ionic
conductivity, decreased proton affirdty for water, radical formation in the
membrane (which can destroy the solid polyrner electrolyte membrane
chemically), loss of mechanical strength via softening of TFE, and increased
parasitic losses through high fuel permeation_
Additionai problems with Nafiant) membranes have been observed in
liquid feed direct methanol fuel ceii applications, where excessive methanol
transport (which reduces power density) occurs. Methanol-crossover not
only lowers fuel utilization efficiency but also adversely affects the oacygen
cathode performance, significantly lowering cell performance_
The Na.fion membrane/electrode is also very expensive to produce,
and as a result it is not (yet) comrzsercially viable. Reducing membrane cost
is crucial to the commercialization of SPEFCs. It is estimated that
membrane cost must be reduced by az least an order of magnitude from the
Nafxon4D model for SPEFCs to become comxnercialty attractive.
Another type of ion-conducting membrane, Gore-Select
(commercially available from W.L. Gore), is currently being developed for fuel
cell applicarions_ Gore-Select membranes are further detailed in a series of
U.S. Patents (U.S. 5,635,041, 5,547,551 an.d 5,599,614).
Gore discloses a composite membrane cozisisting of a Teflon
fluoropolytner ftlna fiiled with a Nafion(V ion-conducting solution. Although
it has been reported to shovi high ionic conductivity and greater
dimensional stability than Nafton membranes, the Teflon and Nafion
materials selected and employed by Gore as the film substrate and the ion-
exchange material, respectively, may not be appropriate for operation in.
SPEFCs. Teflon undergoes extensive creep at temperatures above 80 C,
and Na.fion swells and softens above the same temperature. This caa
result in the widexlin.g of interconnected channels in the meznbrane and
atlow perfor=nance degradation, especiaIly at elevated temperatures and
pressures.
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Further, Gore-Selecttt, as well as many other types of perfluorinated
ion-conducr5ng membranes, are just as costly as NafionO, since these
membranes also use a high percentage of Nafion(b and Nafion -lfke
ionomers.
' ,.
In an effort to reduce costs and move toward potential
cor.uaxerciaiizatiozx of SPEFCs, ion-exchange membranes that are less
expensive to produce also have been investigated for use in polymer
electrolyte membrane fuel cells.
Poly(trifluorostyrene) copolymers have been studied as membranes
for use in poZvmer electaroiyie membrane fuel celis. See e.g., U.S. Patent No.
5,422,411.
Sulfonated poly(aryl ether ketones) developed by Hvechst AG are
described in European Patexit No. 574,891,.A2. These polymers can be
cross-linked by prin-zary and secondary amines_ However, when used as
membranes asid zested in polymer electrolyte membrane fuel cells, only
modest cell performance is observed. Sulfonated polyaromatic based
systems, such as those described in U.S. Patent Nos. 3,528,858 and
3,226,361, also have been investigated as membrane materials for SPEFCs.
However, these materials suffer from poor chemical resistance and
mechanical properties that Iimit their use in SPEFC applications.
Solid polymer membranes comprising a su3fonated poly(phenvlene
ozdde) alone or blended with poly(vinylidene fluoride) also have been
investigated. These membranes are disclosed in WO 97/24777. However,
these membranes are lrnown to be especially vulnerable to =degradation from
peroxide radicals.
The inherent problems and limitations of using solid polytta.er
electrolyte membranes in eiectroehemical applications, such as fuel cells, at
elevated/high temperatures (> 100 C) have not been solved by the polymer
electrolyte membranes known in the art. Specifically, maintaining high iorl
conductivity and high mechanical strength, resisting dehydration and other
forms of degradation remain problematic, especially at elevated operating
tem,peratures_ As a resuYt, commercialization of SPEFCs has not been
realized.
it would be bigh.ly desirable to develop an improved solid poYymer
electrolyte membrane with high resistance to dehydration, high mechanical
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strength and stability to temperatures of at least about 100 C, more
preferably to at least about 120 C.
It would also be highly desirable to develop a membrane with the
afore-znentioned characteristics that would be suitable for use in a hydrogen
or methanol fuel cell and that would provide an economical option to
currently available membran,es. The development of such a membrane
would promote the use of SPEFCs in a variety of highly diverse military and
commercial applications, and would be beneficial to industry and to the
environraent.
SUMMARY OF T$E INVENTxON
The present invention provides innovative solid polymer electrolyte
membranes that are capable of operating ai much higher temperatures and
pressures than those known in the art. Methods for producing such
membranes are also provided. The r.uembrane mataufacturing technologies
developed emphasize improved performance at reduced cost_
A central object of ttie invention is to provide an improved solid
polymer electrolyte membrane (SPEM) having the foIIowing characteristics:
high ionic conductivity, high resistance to dehydration, high mechanical
strength, chernical stability during oxidation and hydrolysis, low gas
permeability to limit parasitic losses, and stability at elevated temperatures
and pressures.
Another object of the invention is to provide an improved solid
polymer electrolyte membrane with electronic conductivity approaching
zero, dimensional stability, and a membrane that is non-brittle in both dry
and wet forms.
Another object of the invention is to provide an improved solid
polyiner electrolyte membrane that is resistant to methanol cross-over when
used in a direct methanol fuel cell.
Another object of the invention is to lower the overaIl cost of
producing solid polymer electrolyte membranes to allow for
commercialization of SPEFCs_
A further object of the invention is to provide methods that can be
employed to produce these solid polymer electrolyte membranes.
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Another object of this invention is to provide novel polymer
substrates and ion-conducting znaterials and novel combinations thereof.
Yet another object of the present invention is to provide SPEMs that
are substantially stable to temperatures of at least about 100 C, preferably
to at least about 150 C, more prefera.blv to at least about 1?5 C_
It has been discovered that a high perFormance SPEM, suitable for
use in fuel cells, can be produced by interpenetrating a porous polymer
substrate with an ion-conducting material to form a composite membrane.
This composite ion-conducting membrane will exhibit the strength and
thermal stability of rhe polymer substrate and the excellent ionic
conductivity of the ion-conducting material..
The composite SPEM of the present invention comprises a porous
polymer substrate that is interpenetrated with an ion-conducting material_
The present invention also provides novel substrates and novel
substrate/ion-conducting material combinations. These materials can be
tailored and combined to produce membranes useful over a range of
operating conditions and/or applicatio7as_
Preferred polymer substrates are easily synthesized from com=ercially-
avail.able,low-cost starting polymers, into thin, substantially
defect free polymeric films which have high strength even at low thickness
(in preferred embodiments less than about 1 mil), outstanding crease/crack
resistance and high tear strength. Preferred polynzer substrates are
substantiallv chemica,lly resistant to acids, bases, free radicals and
solvents
(i.e., smethanol) and are thermally and hydrolytically stable from
temperatures of about 50 C to 300 C. Preferred polymer substrates possess
exceptional mechanical properties (much greater than about 2,500 psi
tensile, much less than about 100% elongation to break), dimensional
stability, barrier properties (to methanol, water vapor, oxygen and hydrogen)
even at elevated temperatures and pressures and exceptionaI gauge
uuiformity (+/- 0.2 mils preferable). In preferred embodiments, the polymex
substrates are thermally and hydrolyticaily stable to temperatures of at least
about100 C.
Preferred polymer substrates have a pore size range of 10 A to 2000 A
more preferably 500 A to 1000 A. and have a porosity range from about 40%
to 90%.
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In some preferred embodiments of rhe present mvention., the polymer
substrate of the SPEM comprises a ivotropic liquid crystalline polymer, such
as a polyber+zazole (PBZ) or polyaramid (PAR or I{evlar ) polymer. Preferred
polyber.izazole polymers include polybenzoxazole (P130), polybenzothiazole
(PBT) and polybenzimidazole (PBI) polymers. Preferred polyaramid polymers
include polypara-phenylene terephthalimide (PPTA) polymers.
In other preferred embodiments, the polymer substrate of the SPEM
comprises a thermoplastic or then-noset aromatic polymer. Preferred
aromatic polymers include; polysulfone (PSU), polyimide (PI), polyphenylene
oxide (PPO), polyphenylene suifoxide (PPSO), polyphenylene sulfide (PPS),
polyphenylexie sulfide sulfone (PPS/S02). polyparaphenylene (PPP),
polypheny3quinoxaline (PPQ), polyarylketone (PK) and polyetherketone (PEK)
polymers.
Preferred polysulfone polymers include polyethersulfone (PES),
polyetherethersulfone (PEES), polyaryisulfone, polyaryletklersulfone (PAS),
polyphenylsulfone (PPSU) and polyphenylenesulfone (PPSO2) polymers.
Preferred polyiznide polymers include the polyetherimide polynm,ers as well as
fluorinated (5 membered ring) polyimides. Preferred polyetherketone
polymers include polyetheretherketone (PEEK), polyetherketone-ketorie
(PEKK), polyetheretkierketone-ketone (PEEKIK) and
poiyetherketoneetherketone-ketone (PEKEKK) polymers.
Preferred ion-conducting materials for use in the fuel cells of the
present invenuon are easily sulfonated or synthesized from commercially-
available, low-cost stazting polvmers, and are swellable, but highly insoluble
in boiling water (100 C) or aqueous methanol (>50%) over extended time
periods.
Preferred iorn-conducting materisls have limited methanol
permeability (limited methanol diffusivity and solubility) even at elevated
temperatures and pressures, are substantially cheipicaD.y stable to acids
and free radicals, and ther=ally/hydrolytically stable to temperatures of at
least about 1000C. Preferred ioxi-conducting matezxals have an ion-exchange
capa.city (IEC) of >1.Omeq/g dry nnernbrane (preferably, 1.5 to 2.Omeq/g) and
are highly ion-conducting (preferably, from about 0.01 to about O_5S/cm,
more preferably, to greater than about 0.1 S/cm or <lOS2cm resistivity).
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Preferred ion-conductirng materials are easily cast into films and/or
imbibed into the polymer substrate. Such films are durable, substantially
defect-free, and dimensionallly stable (less than about 20% change in
dimension wet to dry), preferably even above temperatures of at least about
100 C. Particularly preferred ion-conducting materials have the ability to
survive operation in fuel cells (i.e., Hz/Oz, methanol) for at least about
5O00
hours (automotive).
In one preferred embodiment of the present invention, the ion-
conducting material of the SPEM comprises a sulfonated, phosphonated or
carboxylated ion-conducting aromatic polymer or a perIIuorinated ionomer.
For example, it may comprise a suifoxiated derivative of at least one of the
above-listed thermoset or thermoplastic aromatic polymers. It may also
comprise a sulfonated derivative of a polybenzazole or polyararnid polyzner.
In an altemate embodiment, the ion-conducting material of the SPEM
of the present invention comprises a non-aromatic polymer, such as a
perfluorina.ted ionoazer. Preferred ionomers include carboxyl-, phosphonyl-
or sulfonyl-substituted pezfluorinated vinyl ethers.
Other preferred ion-conducting material.s for use in the present
invention include polystyrene sulfonic acid (PSSA), polytrifluorostyrene
sulfonic acid, polyvinyl phosphonic acid (PVPA), polyvinyl carboxylic acid
(PVCA) and polyvinyl sulfonic acid (PVSA) polymers, and metal salts thereof.
Substrate and ion-conducting materials for use in the present
invention may be substituted or unsubstituted and may be homopolymers
or copolymers of the polymers listed above. Representative formulae of the
unsubstituted monomers can be found in Tables 4 to 7 at the end of the
Detailed Description of the Invention.
Followang selection of a suitable polymer substrate and ion-
condueting material in accordance with criteria set forth herein, one
preferred method of fabricating a membrane of the present invention
comnprises the foIIoaring steps: solubiiixing the ion-conducting material,
preparing a polym.er substrate membrane, swelling the membrane with
water, solvent e;cchanging the water swollen membrane, imbibing the
solvent swollen substrate with the ion-conducting material via solution
infltration such that the microinfrastructure of the porous polymer
substrate is substantially interpenetrated with the ion-conducting
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material. Upon solvent evaporation and drying, the microporous
substrate will collapse locldng the ion-conductor within the
microinfra.structure of the polymer substrate. Post imbibing steps may
include tension drying, stretching and hot pressing of the coznposite
membrane. The substrate provides mechanical and chemi.ca] stability,
while the ion-conductor provides a high-flux proton path. The SPEMs
of the present invention also act as a barrier against fuel (H2, O2 and
methanol permeation) in fuel cell applications.
Another preferred method of producing the membranes of the
present invention comprises the steps of preparing a mixture of the
porous polynner substrate and the ion-conducting material in a
common solvent and casting a coznposite membrane from the mixrure.
Preferred solvents for these methods include tetrahydrofuran (THF),
dimethylacetamide (DMAc), diznethylformamide (DMF),
dimethylsulfwcide (DMSO), N-Methyl-Z-pyrrolidinone (NMP), sulfuric
acid, phosphoric acid, chlorosulfonic acid, polyphosphoric acid (PPA)
arnd =nethanesulfonic acid (MSA). PPA/MSA are preferred solvents for
a polymer substrate and ion-conducting material combination of
PBO/PPSU.
Still another method of producing a membrane of the present
invention comprises the steps of sulfonating the pores of the polymer
subsrrate with a sulfonating agent.
Yet another naethod of producing a znembrane of the present
invention comprises the steps of preparing a mixture of a porous
polymer subsuate and an ion-conducting material and extruding a
composite film directly from the niiz*+ -e.
The membranes of the present invention are useful in a variery
of electrochemical devices, including fuel cells, electronic devices,
systems for membrane-based water electrolysis, chloralkali
electrolysis, dialysis or e3.ectrodialysis, pervaporation or gas separation.
The foregoing and other objects, features and advantages of the
invention will become better understood with reference to the following
description and appended claitns.
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BRIEF pESC32IPTION OF THE DRAWINGS
Fig. I is a schematic illustrating the preparation of a composite m.embrane of
the present invention.
Fig. 2 shows a graph of % dry loading of ICP/PBO vs. initial ICP
solution wt% for NafiorxtV/PBO, Radel R /PBO and Sulfide-Sulfone/PBO, in
accoardance with the present invention.
p~'r'AILED DESCRII'TION
The composite membranes of the present invention are designed to
address the present shortcomings of today's solid polymer electrolyte
membranes, specifically Nafion(b and other like membranes (e_g., Gare-
Select ).
The present invention provides a relatively low cost, composite solid
polymer electrolyte membrane (SPEM), with improved power density and
reduced sensitivity to carbon rnono:dde in hydrogen fuel. It also alleviates
water management problems which limit the efficiencv of present Naia.onO
membratne-based fuel cells_
The composite membranes of the present invention may be employed
in variAous applications, including but not limited to, polarity-based
chemical
separations; electrolysis; fuel cells and batteries; pervaporatiori; reverse
osmosis - water purification, gas separation; dialysis separation; industrial
electrochemistry, such as choralkali production and other eleetrocheoaieal
applications; water splitt u~.is g and subseauent recovery of acids and bases
from waste water solutions; use as a super acid catalyst; use as a medium
in enzyme immobilization, for example: or use as an electrode separator in
conventional batteries.
The composite SPEMs of the presezrt invention comprise a porous
polymer substrate interpenetrated with an ion-conducting material. Tbe
porous polymer substrate serves as a mechanically, thermally, chemically
and oxidatively durable support for the ion-conducting material, e.g.,
poiyruer_ Ion-conducting polymers (ICPs) with very high ion-e_change
capacities (IEC>2.0 meq/g) can be used in SPEMs of the present invention,
since the strength properties of the ICP are not needed for mem.brane
mechanical integrity. These ion-exchange polymers with higher degrees of
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sulfonation than typical Nafion and NafionO-like materials, wii1 possess
correspondingly higher values for ionic conductance.
The porous polyrner substrate is characterized by a
microirnfrasuucture of channel.s that have substantiaIly uniform.
unchanging dimensions (Tg is higher than use temperature). That is, the
substrate material will not flow, since the operating temperature is less than
the Tg of the substrate. The ion-conducting polymer substantially
interpenetrates the rnicroixxfrastructure of the porous polymer substrate-
This configuration, which can be made quite thin, promotes efficient proton
transport across the membrane and rn+n;n+2zes water management
problems- As a consequence, eventual membrane dehydrauon, parasitic
losses and loss of ionic conductivity can be substantially prevented-
Preferably, thermally stable, wholly aromatic polymers are used in
producing the composite membranes of the present invention, but any
material(s) meeting the following requirements rnay generaIly be used- low
cost, high ionic conductiviLy, electronicaIly insulating, irnpernaeable to
fuel
(H2, 02, naetha.nol) permeation at elevated temperatures and pressures in
fuel cell applications, chemically resistant to acids, bases and free
radicals,
Tg above fuel ceit operating temperature (at least about 175 C is preferred),
** nimal water transport rate during operation, resistance to puncture or
burst during operation at high temperatures and pressures, and
tnaintenance of ionic conductivity at elevazed/high operating temperatures.
The selection criteria for polymer substrates and iorn=conductin.g
materials suitable for SPEMs of the present invention are described below.
Structures for preferred polymer substrates and ion-conducting polymers
are indicated in Tables 4 to 7 which appear at the end of this section.
Preferred polymer substrates are easily synthesized frotn.
commerriaIIy-available, low-cost statting polymers, into thin, substantially
defect free polymeric films which have high strength even at low t.hickness
(preferably less than about 1 ini1,), outstanding crease/crack resistance and
high tear strength. Preferred polymer substrates are substantially
chemically resistant to acids, bases, free radicals and solvents (i.e.,
methanol) and are thermally and hydrolyticaIly stable from tempera.tures of
about 50 C to 300 C. Preferred polymer substrates possess exceptional
mechazucal propercies (much greater than about 2,500 psi tensile, much
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less than about 100% elongation to break), dimensional stability, barrier -
properties (to methanol, water vapor, oxygen and hydrogen) even at elevated -
temperatures and pressures and exceptional gauge uniformity (+/- 0.2 mils
preferabie)_ In preferred embociiments, the polymer substrates are
thermally and hydrolyv.caliy stable to temperatures of at least about 100 C.
Preferred polymer substrates have a pore size range of 10 A to 2000 A
more preferably 500 A to 1000A, and have a porosity range from about 40%
to 90%.
In some preferred embodunents of the present invention, the porous
polymer substrate of the SPEM comprises a lyotropic liquid crvstalline
polymer, such as a polybenzazole (PBZ) or polyaramid (PAR or KevlarO)
polymer. Preferred polybenzazole polymers include polybenzoxazole (PBO),
polybenzothiazole (PBT) and polybenzixnidazole (PBI) polymers. Preferred
polyaramid polymers include polypara-phenylene terephthalamide (PPTA)
polymers. Structures of the above-mentioned polymers are listed in Table 4.
In other preferred embodiments, the porous polymer substrate of the
SPEM comprises a thermoplastic or thermoset aromatic polymer. Preferred
groups of these aromatic polymers include the following: polysulfone (PSU),
poly.unide (PI), polyphenylene oxide (PPO), polyphenylene sulfoxide (PPSO),
polyphenylene sulfide (PPS), polyphenylene sulfide sulfone (PPS/SOx),
polvparaphenylesie (PPP), polyphenylquinoxaline (PPQ), polyarylketone (PK)
and polyetherketone (PEK) polyrners.
Preferred polysulfone polymers include polyethersulfone (PES),
polyetherethersulfone (PEES), polyarylsul.fone polyyarylethersulforne (PAS),
polyphenylsulfone (PPSLT) and polyphenylenesulfone (PPSOz) polymers.
Preferred polyimide polymers include the polyetherimide polymers and
fluorinated polyizaides_ Preferred polyetherketone polymers include
polyetheretherketone (PEEK), polyetherketone-ketorae (PEKIq,
polyetheretherketone-ketone (PEEKK) and polyetherketoneetherketone-
ketone (PEKEKK) polymers. The structures of the above polymers are listed
in Tables 5 and 6 below.
More preferably, the porous polymer substrate comprises a PBO or a
PES polymer. Most preferably, the porous polymer substrate comprises a
PBO polymer, such as a poly(benzo-bisoxazole).
- 14 -
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- ------- ---- --- -
CA 02300934 2005-10-05
The PBO polymer is a member of a relatively new class of polymeric
materials collectively referred to as ordered polymers. As a result of its
rigid-rod-like molecular structure, PBO forms liquid crystalline solutions
from which extremely strong stiff fibers and films have been processed.
Foster-Miller has pioneered the development of innovative methods for
processing PBO into microporous high-strength high-modulus thermally-
stable films that are useful for a multitude of high-performance applications,
e.g., in advanced aircraft and spacecraft.
When the PBO polymer is in a dry (entirely collapsed) form, it has the
following characteristics: high strength and dimensional stability, superior
barrier (gaseous) properties, excellent crease/crack resistance, excellent
tear strength, and superior thermal and hydrolytic temperature stability
(>300 C).
Film-forming processes involve several operations in which a PBO
polymer solution in polyphosphoric acid undergoes a succession of
structural changes, leading to the fmal product form. One basic process for
producing PBO products includes extrusion of the polymer substrate
solution (polymer and acid solvent), coagulation to lock-in the molecular
structure, washing to remove the acid solvent, and drying (at high
temperatures) to remove the exchanged water and consolidate the polymer
into the end product.
In one particularly preferred embodiment, the PBO film is extruded
and multiaxially oriented using a blown process as disclosed, e.g., in U.S.
Patent Nos. 4,939,235, 4,963,428 and 5,288,529. The degree of multiaxial
orientation can be varied from t A of 5 to 65 , though an orientation of 22
to 30 is preferred. ,
During composite membrane fabrication, the following problems may
be encountered: substrate film delamination, iunbibtion of an insufficient
amount of ion-conducting material inside the porous substrate and/or
inability to maintain, if desired, a smooth outer layer of ion-conducting
polymer for proper bonding. These problems may be overcome by heating of
the ion-conducting polymer solution during imbibtion into the substrate
(which decreases the solution viscosity and swells the pores of the
substrate) and using less oriented films (which allows more ion-conducting
material into the substrate, decreased bubble point).
-15-
CA 02300934 2003-09-12
WO 99/10165 PCT/US98/I9898
The polymer substrate processing sysiem includes a hydrolic flask,
extruder, pump, counter-rotating die (CRD). porous ring, water wash
tank/ collapse shed and f'im take-up system. In one embodiment, the take-
up system includes a 3" porous sizing ring followed by a 6" diameter take-up -
roll along with a 4" diameter spooler. A number of CRDs and annular
configurations may be used.
Irxformation is collected and recorded for wet fiJm thiclness, dry fil,m
thickness, draw ratio, blow-up ratio, overall film quality (veins, thin spots,
voids, cracks, etc.) and exttusion system settings.
Samples (wet and dry) of PBO film from each extrusion run are then
tested for tensile strength and tensile modulus, bubble point, pore size
distribution, total pore volume and mean pore size, gas vapor (H20, 02)
per.meability, zinc metal level in polymer.
Interestingly, smaller die gaps have been shown to cause greater
shearing during e-xtrusion, which results in fewer veins (defects) in the PBO
film. High blow-up ratios also have resulted in improved films.
Additionally, smaller die gaps and larger blow-up ratios increase PBO fibril
orientation without the drawback of additional shear from die rotauoxs...
(although torsional stress increases slightly.)
In the coagulation stage, a liquid to solid phase transition is induced
by diffusion of a non-solvent (water) into the PBO solution. During this
phase transition cycle, the final structure of the solid is established. It is
believed that the structure formed during the coagulation stage of PBO fiber
and film is an interconnected network of highly oriented microfibrils of 80 A
to 100 A diameter. Such films have been dried under tension in order to
produce high tensile properties. During the drying process, the micropores
present as spaces between microfibriis in PBO film, undergo substantial
shrinkage decreasing in dimensions from several thousand Angstroms (e.g.,
2000 A) in size to less than 10 A in size for the dried heat-treated PBO
filtn.
The final pore size depends highly upon the heat treatment methods
employed.
In formuig a porous polymer 'substrate of the present invention,
instead of drying the water from the network, the water is replaced by the
desired ion-conducting material.
- ].6 -
suesrrME SHEET (RULE 26)
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CA 02300934 2003-09-12
wo 99no165 PC"T/[JS98l17898
It has been discovered that a high performance PBO fuel cell
membrane can be produced by interpenerxating the interior porosity of
water-swollen PBO filrm' s with concentrated or dilute solutions of ion-
conducting polymers, such as Nafion or polyethersulforne polysulfonic acid.
S For example, after the coagulated PBO fiIan has been irfiltrated with a
Naf ong) solution, the NafionC7 regions within the pores (and coating on the
surface) of the f21rn will form a highly ionically-conducting gelatinous
Naf on O membrane supported by the porous PBQ membrane substrate_
Such SPEMs will exhibit the strength and thermal stability of PBO and the
excellent ionic conductivity of water-swollen Nafion copolymer.
The usual deficiencies of Nafion. , such as membrane weakness and
softening at elevated texnperaLures, are negated by the PBO substrate to
support against compression while simultaneously providing sufficient
porosity to allow for adequate water content, thus enabling high proton
transport. In preferred ernbodaznents, the substrate will accommodate about
40 to about 90 volume percent, preferably about 70 to about 80 voZume
percent of ion-conducting polymer.
As noted above, a second preferred polymer substrate comprises a
PES polymer. PES is a high use temperature amorphous thermoplastic that
exhibits long-term stability at elevated temperature (> 175 C). The
microporous PES substrate represents a new class of high perfox-.ma,nce fuel
cell membranes that Ga-a be used to solve the difficulties inherent in current
Nafion membranes as discussed above.
PES is readily available from Amoco Performance, Iac. in Al.pharetta.,
2S Georgia, USA, in large quantity at low cost and exhibits the combinatioa of
desirable properties required for efficient function at much higher
temperatures and pressures than are now possible (potentially greater than
about 175 C temperature and greater than about 100 psi gas pressure).
Microporous PES Mns for use in the SPEMs of the present invention
can be produced via standard film casting techniques or purchased directly
from appropriate vendors. As with other suitable polymer substrates, in one
preferred embodiment, PES is dissolved iin an appropriate water-miscible
solvent to a predetermined concentration. A wt.% solution of PES is
selected to produce a film with minimized thickness (preferably less than
about 1 mil)_ The PES solution is then cast onto glass plates to form a film,
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SUBSTTTl1"t'E SHEET (RULE 26)
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wU 99/10165 pCI'lUS98/I7899
e.g., about 0.5 mil thick. lxnrnersion of the plates in water coaguiates the
polymer and leaches out the solvent forming the microporous substrate
membrane in a water swollen state. The ion-conducting polymer can then
be introduced into the microporous voids of the water swollen PES substrate
membrane using solvent exchange processes to forra the composite
membrane. Alternatively, the membrane can be dried first and then
infltrated with the ion-conducting solution using vacuum to remove air
bubbles and fill the pores with NafionO_ The membrane may also be
produced by an extrusion process as described herein.
I0 Preferred ion-conducting polymers for use in the present invention
are easily sulfonated or synthesized from cornmercially-available, low-cost
starting polysners,-and are swellable, but highly insoluble in boiling water
(100 C) or aqueous methanol (>50%) over e.'ctended time periods. Preferred
ion-conducting polymers have IimiLed methanol permeability (limited
methanol diffusivity and solubility) even at elevated temperatures and
pressures, are substaxztiallv chemically stable to acids and free radicals,
and
therznaLly/hydrolytically stable to temperatures of at least about IO0 C.
Prefcrred ion-conducting polymers have an ion-exchange capacity (IEC) of
> 1.Osneq/ g dry mern,brane (preferably, 1.5 to 2.Omeq/ g) and are higk2ly ion-
conducting (preferably, from about 0.01 to about 0_5S/cm, more preferably,
to greater than about 0.1 S/cm or < l0t2czn resistivity). Preferred ion-
conducting polyraaers are easily cast into filia~.' s and/or imbibed into the
polymer substrate_ Such films are durable, substantially defect-free, and
dimensionally stable (less than about 20% change in dimension wet to dxy)
even above temperatures of at least about 100 C_ Preferred ion-conducting
polymers have the ability to survive operation in fuel cells (i.e., H2/02,
methanol) for at least about 5000 hours (automotive).
Preferred ion-conducting polymers are substanti.ally chemically stable
to free radicals. Cross-linkzng methods or the use of additives can also
provide or enhance peroxide stability.
The peroxide (H2O2) screening test serves as an accelerated fuel cell
life test_ The test simulates long term fuel ceII operation by exposing the
subject aqueous ion-conducting membrane to a peroxide/iron solution at
68 C for 8.0 hours. Under these conditions, aggressive hydroperoxide
(HOO-) radicals are produced. It has been shown that these radicals are
- 18 -
SU6SSITU?'E SHEET (RULE 26)
CA 02300934 2005-10-05
formed during normal H2/02 fuel cell operation, and are the prominent
membrane degradation mechanism.
Polymer additives have also been evaluated that can be used as
radical scavengers within the ion-conducting component of the SPEMs of
the present invention. Examples of these include Irgano.-e 1135
(commercially available from Ciba Geigy) and DTTDP (commercially available
from Hampshire). In addition, the ion-conducting component polymer can
be cross-linked via heating to slow membrane degradation.
In one preferred embodiment of the present invention, the ion-
conducting material of the SPEM comprises a sulfonated (SO3H),
phosphonated (PO(OH)2) or carboxylated (COOH) aromatic polymer. For
examples of phosphonates, see Solid State Ionics, 97 (1997), 177-186. For
examples of carboxylated solid polymer electrolytes, see Solid State Ionics,
40:41 (1990), 624-627. For example, the ion-conducting material may
comprise a sulfonated derivative of at least one of the above-listed thermoset
or thermoplastic aromatic polymers. It may also comprise a sulfonated
derivative of a polybenzazole or polyaramid polymer.
Though sulfonated polymers are not readily available in industry, the
synthesis of such polymers is well known to the skilled artisan and can be
found in various patents and publications. See for example, U.S. Patent
Nos. 4,413,106, 5,013,765, 4,273,903 and 5,438,082, and Linkous, et al., J.
Polym. Sci., Vol. 86: 1197-1199 (1998).
In an alternate embodiment, the ion-conducting material of the SPEM
of the present invention comprises a non-aromatic polymer, such as a
perfluorinated ionomer. Preferred ionomers include carboxyl-, phosphonyl-
or sulfonyl-substituted perfluorinated vinyl ethers.
Other preferred ion-conducting materials for use in the present
invention include polystyrene sulfonic acid (PSSA), polytrifluorostyrene
sulfonic acid, polyvinyl phosphonic acid (PVPA), polyvinyl carboxylic acid
(PVCA) and polyvinyl sulfonic acid (PVSA) polymers, and metal salts thereof.
More preferably, the ion-conducting material comprises a sufonated
derivative of a polyphenylsulfone (PPSU), polyethersulfone (PES), polyimide
(PI), polyphenylene sulfoxide (PPSO) and polyphenylenesulfide-sulfone
(PPS / SO2) . These polymers and additional preferred polymers are listed in
Table 7.
Trade-mark
-19-
CA 02300934 2005-10-05
In order to facilitate interpenetration of the ion-conducting polymer
into the pores of the polymer substrate, surfactants or surface active agents
having a hydrophobic portion and hydrophilic portion may be utilized in
promoting the interpenetration of the ion-conducting polymer into the pores
of the polymer substrate. These agents are well known in the art and
include Triton X-100 (commercially available from Rohm & Haas of
Philadelphia, PA).
Compatibilizers may also be employed in producing composite
membranes of the present invention. As used herein, "compatibilizers" refer
to agents that aid in the blendability of two or more polymers that would
otherwise be resistant to such blending. Examples include block
copolymers containing connecting segments of each component. These
include potential substrate and/or ion-conducting polymer components.
The SPEMs and methods of the present invention will be illustrated
by specific combinations of polymer substrates and ion-conducting
polymers. However, the present invention should not be construed as being
limited in use to any particular polymer substrate or ion-conducting
material. Rather, the present teachings are suitable for any polymer _
substrate and ion-conducting material meeting the criteria set forth herein.
Several different innovative methods have been developed for
producing the solid polymer electrolyte membranes of the present invention
by providing a polymer substrate interpenetrated with an ion-conducting
polymer. Each method is lower in cost and higher in efficiency than current
methods of producing Nafion (or Nafion -like) membranes. These methods
include imbibing a porous substrate membrane with an ion-conducting
material, casting a composite membrane from a common solvent,
sulfonating the pores of a suitable polymer substrate to form a composite
SPEM of the present invention, and extruding a composite film directly from
the mixture of a polymer substrate and ion-conducting material.
The first method uses Nafion as an example of a suitable ion-
exchange material, in order to demonstrate the clear advantage of using the
composite SPEM of the present invention.
Initially, a porous membrane having the djesired pore size and pore
content is made using a suitable polymer substrate, e.g., PES or PBO.
Either casting or extrusion processes are utilized to produce these
* Trade-mark
-20-
CA 02300934 2003-09-12
_c . ..
. ~. ~1
WO 99/10165 PC.T![JS98l17898
membranes as described above. The pores of the porous polynier substrate
meznbrane are theri i.nterpenetrated with an ICP, e.g.. solubilized Nafion+D
ion-conducting polymer. The Nafion -interpenetrated porous membrane is
then immerscd into a dilute acid reieasing the insoluble free sulfonic acid
form of Nafion as a high ionica2ly conducting gel within the micropores and
as thin coatings oa, the surfaces of the membrane. The flexible, pressure-
resistant, high Tg, porous substrate provides puncture and crush-resistance
to the thin coating of ion conductor membrane and also to the Naflon4-filled
mucropores even at temperatures above 1?5 C (the Tg of PES is 220 C, PBO
has no Tg).
Composite membrane porosity is controlled during the irnbibtioan
processes by varying the %wt. of ior.i-conducting material isr, solution to
produce a membrane with numerous pores (preferably m.i.croscopic) of
substantially uniform dimensions (preferably < about 1000 A).
The remainder of this page is intentionally left bL-nk.
21 SUt35TfTUTE SHEET (RULE 26)
----------------
CA 02300934 2003-09-12
Ir
WO 99110165 pCOUSg~7898
A comparison of physical chemical properties of Naf'ioxn 117 and
SPEMs of the present invention follows in Table 1 below.
TABLE 1
=
PROP'ERTY NAFION 117 SPEMS OF TSE
PRESENT UNMiTION
Thickness (nmil) - wet 6 to 8 -=0.1 to -5_0, preferably =
H+ resistance (ohm-cra) 10.0 -5.0 to -100.0,
preferably <-10.0
Tensile (psi) at break 2500 to 2700 -2500 to -50,000,
preferably >-10,000
Elongation (%) at break 110 to 130 -5 to -20, preferably
<-.15
% water coxatent* (based on 35 to 40 -20 to -100, preferably
dry weighL of membrane) <-50
Ion-exchange capacity 0.8 to 1.0 -0.2 to -2.0, preferably
(meq/g dry SPE) -1.5 to =-2.0
Methanol perineability (cm3- 0.01 preferably -0.01
secl
H2 permeability 600 -60 to -600, preferablv
(cm3_nvl/ft2 hr-atm) -600
02 permeability 330 -30 to -330, preferably
(cm3-mfl/ft2 hr-atm) -330
Hydrodynamic H20 50 -5 to -50, preferably -50
permeability
CI213-rA11 ft 2112'-atlII)
Electxo-osmotic HaC 7.5 x 10-4 --
permability
cm3-co,alornb7
MivLimum temperature ( C) of -100 -100 to -175, preferably
thexmal/hydrolytic stabili.ty -150
Diumensional siability- dry to <20% 0 to -20%, preferably
wet expansion of inembrane <..20 /o
Ionom.er degZ-adauon: <10% 0 to -20%, preferably
(accelerated ]ife testi.ngj <_100/,
Chemicaal stability: 20,000 -250 to -5000
oxidation and hydrolysis
useful life, hours
Crease/crack Pass Pass
(ability to withstand
five folds in hydrated or
state
cbr
Tear strength Pass Pass
(ability to withstand tear.ing in
h drated or dry state
"Mesnbrane hydrated soakin in 100 C H20 for 1 hour
-22-
SUesTrTUTE SHEET (RULE 25)
CA 02300934 2003-09-12
wo 9911oib5 PCrI[IS98r17s9S
In one preferred embodiment, the polymer substrate is dissolved in =
an appropriate water-miscible solvent to a predetenained concentration. The
wt.% solution of polymer substrate is selected to produce a fsIm with
mi_r, +~ed thickness (preferablv <lsuil). The polymer substrate solution is
then cast onto glass plates to form -0.5 mil thick film. Immersion of the
plates in wazer coagulates the polymer and leaches out the solvent forming
the microporous substrate membrane in a water swollen state. Nafion (or
other ion-conducting polymers) can then be introduced into the
microporous voids of the water swollen substrate membrane using solvent
exchange processes to forrrt the composite membrane. Alternativelv, the
membrane can be dried first and then infiltrated with NafionCv solution
using vacuum to remove air bubbles and fill the pores with Nafion(g. The
membrane may also be produced by an extrusion process as described
herein.
In a second preferred embodiment of the invention, porous polvmer
subsrrate membranes containing an ion-conducung material can also be
produced by casting the membranes from a coznmon solution containing
appropriate concentrations of the polyuxer substrate and ion-conduchng
material. Determination of %wt- ion conductor/%wt. substrate are based
on the desired final thickness, % voluzne of ion-conducting polymer and the
particular polyzaers employed_ In some instances, this process may produce
composite membranes in which the ion-conducriszg polymer domain sizes
are smaller and more uniform than in composite membranes produced by
imbibing pre-forined porous substrate membranes. In this process, pore
size and content can be more easily controlled in the membrane by
adjustment of individual component concentrations. The %wt. of the
solution is adjusted to obtain the desired composite. In one embodiment,
the ion-conducting polymer solution can be prepared by dissolving the ion-
conducting polyzner in sulfonate salt form in hot alcohol/water mixtures
(e.g., Nafion 1100 EW solution, 5% from Dupont),
Preferred cosolvents include, but are not limited to, the following:
tetra,hydrofuraan (THF), di.methylaceta,mide (DMAc), dimethylformamide
(DMF), dim.ethylsulfoxlde ('DMSO), N-Methyl-Z-pyrrolidinone (NMP), sulfuric
acid, phosphoric acid, chlorosu3fonic acid, polyphosphoric acid (PPA) and
- 23 -
suesTlruTE SH"-? (iiuuE 25)
CA 02300934 2003-09-12
wo "110165 pu1'rMsMs9s
methanesulforuc acid (MSA). 'I'PA/MSA are preferred solvents for a polymer-
substra.te and ion-conducting material combination of PBO/PPSU.
In a third preferred embodiment of this invention, a polymer
substrate is chemically sulfonated to produce a sulfonated composite
in situ- This coa.cept draws on a number of technologies. A variety of
methods exist for the fabrication of porous polymer films, most
centered around dissolving a polymer within a water miscible solvent.
A freshly cast film is then soaked in water causing the polymer to
precipitate from solution. This phase separation of the solvent and the
polymer ca.uses the fortuation of the porous network as the solvent is
leached into the water. One example would be the formation of the
PBO polymer substrate, but this can be extended to a Iarge number of
polymers. One typical method for suifonating polymers is direct
exposure to concentrated sulfuric acid (esp. at elevated temperasures).
Imbibing a sulfuric acid solution into the porous polymer network,
followed by rapid heating to high temperatures (250-350 C) has been
shown to suZfonate the polymer. If a dilute acid solution is used, the
polymer vriJl not dissolve in the sulfonating process. As a result, only
the surface within the porous network will be sulfonated. The pxoduct
is a composite suucture of unsulfonated polymer with sulfonated
polymer on the surface.
In a fourth preferred embodiment, a solid polymer electrolyte
composite membrane of the present invention can be made by preparing a
mixture of a polymer substrate and an ioa-conducting polymer and
extruding or casting a composite film directly from this ra.ixiure.
One way to realize the direct extrusion of a solid polymer electrolyte
composite membrane without inbibing a porous polymer substrate with an
ion-conducting polymer solution would be the fine dispersion of one
component in a solution of the other. Provided the solvent used would only
dissolve one of the components, a composite could be obtained by eatttxding
or casting this physical mixture of the components followed by removal of
the solvent-
Another possibility would be the dissolution of both components in a
conirnon solvent. A composite membrane would be formed with the phase
separation of the components, either before or after the removal of the
- 24 -
SU6STTRfTE SHEET (RULE 26)
_ .....'-.-..-._._..__.___. .__
CA 02300934 2003-09-12
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wo 99no165 PCTlUS98/I7898
solvent. Sirailarly, many polymers can be uniformly blended in the melt
(e.g. without solvent). However, upon cooling the components may phase
separate into the appropriate interpenetrating network (IPN)-type structure.
This last method would also be useful from the standpoint that no solvent is
required.
Examples of these methods include blending of suifonated and
unsu]fonated versions of one polyxuer in the high temperature melt, followed
by their phase separation on cooling. The typical solution of PBO in
polyphosphoric acid would dissolve the ion-conducting polymer_ Fibers of a
suitable polymer substrate could be dispersed into a solution (or melt) of the
ion-conducting polyxmer_ Exuttsion or casting of this niixWre, followed by
removal of the solvent would provide a typical fiber reinforced composite
structure.
Optimal interpenetration of the polymer substrate by the ion-
conducting polymer is estimated to be in the range of 40-90% volume. More
preferably, interpenetration is in the range of 70-80% volume. Percent
values can be deterrained by comparing the thickness of a membrane
infiltrated with ion-conducting polymer with a control membrane with no
infiltration. (For example, double thickness would indicate 50%
interpenetration.) General, microscopic techniques are employed in this
determinatiors_ For e_-cample, in the case of PBO polymer substrates, this
m.easureznent was achieved by swe]ling a PBO membrane in water and
replacing the water with the ion-conducting polymer.
The remainder of this page is fittentionally left blank.
SUbS'ft7'U?E 5HEEY (F3ULE 25)
CA 02300934 2003-09-12
~U 99110163 PLT/US98/17898
The following tables further illustrate SPEMs of the present invention.
TABLE 2
Comparacive Data for Water and Methanol Transmission Experiments
SAMPLE- Film: Film: Avg. Avg- Avg. Material 2 ffiZ 1 HR WVTR WVTR meOnT2L
Type Water Boiling (25 C) (80 C) (25 C)
Uptake Water gl(aail* g/(mil*10 g/(ma1*
(%) Uptake 100in2 Oin2 *24 1001n2
(~'' - "24 hr hr *24 bs
Unsulfonated 0.00 1.20 5.7 106.0 NT
Udtl PES
50% 8.70 3.23 47.3 673.0 NT
Sulfonated
Udel PES (FM
75% 12.12 11.94 29.1 814.4 NT
Sulionated
Uder PES (FMI)
85 i 12_50 92.70 116.2 2850.0 NT
Sulfortated
Udel PES (FMI)
1000/0 1074.6 462.25 109.30 3095.3 288.1
Sulfonated PES 8
in PBO
Nafion 117 16.88 35.34 1003.10 15200.4 2680.1
Control
PBO Control 0.00 0.30 0.0 4.1 NT
NT = Not Tested
The following table shows comparative data for membrane properties
for PBO/PES-PSA (75%) and PHO/PES-PSA (85%) and Nafion .
TABLE 3
Comparative Data of Membrane Properties
MEMBRANE
PBO/PES-PSA PBO/PES-PSA Nafion
Propeatp (75%) (85%) 117
ThiCkness (mil5 1.5 1.5 7.0
Resistivity 14.7 11.38 9.S - 10.0
ohm-cm
Water content 45 55 35 - 40
IECan. sue 0.55 0.96 0.91
-26-
SUBSTITUTE SHEET (RULE 25)
CA 02300934 2003-09-12
-- .. = - ~~- ..
-wo 9sn0165 PCTNS98/17898
TABLE 4
Nafion
fCF2 CF2 ~CF2 ( X y
Q
CF_ ~F2O'Cfi2'CF,-SO3
CF2
PBO (poly(bisbenzoxazole))
o ~,, o~
N~.='", N
PBT (poly(benzo(bis-thiazole)-
1.4-phenyler.ee)) N ~ s
S ~ I N -
PBI (poiy(bexizo(bis-diazole)-
1,4-phenyiene) N >-J-
PAR '" N ~ (polyaramid or KevZaz )
O O H H
G N N
-2?-
SUBSTITUTE SHEET (RULE 26)
......
CA 02300934 2003-09-12
. . ... t~- ( WO 99110165 PGTNS981i7898
TABLE S
PSU (polysvlfone) CH3 o
11
~ic-a 0~ - O~
c~i3
PES (polyether sulfone) o
1PEES (polyeLher-ether sulfone) 0
s-
\--~ ~--~ 4
PAS (polyarylether sulfone) o
o / \ o / \
PPSU (polypheayiene sulfone)
-28-
SUSSTmrte SHEET (RULE 26)
~.~_. .
CA 02300934 2003-09-12
- , ~ WO 99rno165 rCT1US99n7898
TABY.E 6
PI (polyimide) o 0
N
p O
PPO (polyphezayiene oxide) c143
/~\ on
CH3
PPSO (polyphenylene
sulfoxide)
l_\~1 0
PPS (polyphnylene sulfide)
/~\ s~
PPS/SOa o
(polyphenylenesulfide s~
sulfone) n
PPP (polyparaphenylene)
PPQ (poly(penylquinoxaline) N a
N
O O n
PEK (polyetherketone) +o-cH-
PEEK o
(polyethez-etherketone) /r\ 0 PEKK o
(polyetherketoneketone)
~n
PEEKK o 0
(polyetheretherketone- 0 /\ 0 /r\ o a ct
etone) ~
k
"PEKEKK (polyetherketone- o 0 0
etherketone-ketone) / o 'co a c
29 -
SUBSTI7UTE SHEET (RULE 26)
CA 02300934 2003-09-12
.. / i
WO 9s110165 rcrnJS98n739S
TABLE 7
pEI (polyetherimide) o 0
R=ary1, alkyl, aryl ether or
~'~
o \~
alkylether O
n
Ude1 polysulfone o cW3
ic-0
~
Radel R polyphenylsulfone o
4CO} 11 -~}- O O 4
0
Ra.del A polyethersulfone o
0 ~-=-/ n
and
0
~ s-QoQo3
- poly~trifluoro-methyl-
bis(phthaiimade)-phenyiene) o o -
c I
NI O I 3O N O
O O a
poly(triphenyiphosphine o d
oxide sulfide-phenylsulfone- p-a s~
sulfide) ~ o v
(PBO-pn
poly(beriz(bis)oxazale '~o ~ o~
poly(phenylsulfide 1,4
phenylene)
n
s
-30-
SUBS'ITi11T@ SHEET (RULE 26) -
CA 02300934 2003-09-12
. ' . . . r-~~----
' : .
wo 99110165 . . ' . _ . . ~. . ~'iY ~4-' = -
poly(aifuorommethyl- a cg's o '
bis(phthalimide)- o
O ~3~ u
phenylsulfone N s
~-' o
O
n
(PVSA) polyvinyl sulfonic
acid iH ._ CH2
SOsH
poly(Phthalimide
ditrif],u oromethyl suethylen.e ~'
e~ alimide-l,3-phenylene a c o N Qcc 0
~
poly-x (zna.xdexa)
c=a
0
0
b
poly(pymJznelliuc diimide- o v
1,3-phenylene) \ /
x x ~
o~ ~o ~
,
a
poly(cliphthaliaude-1,3- o 0
phenylene)
=i ~ 1
Q O
(PPO) poly(1,4-phenyieue ff3 o}
wide)
Diphe.n.yi PPO (poly(3,5-
diphenyl 1,4-pheztylene '
oxide)
0
J.
PBPS (poly(beazophenone sulfide)) jo
0S
n
-31-
SUBS7i7VTE SHEET (RULE 26)
---
-- -- 1-~
Sep-12-03 16:17 From-Ridout&frlaybea CA 02300934 2003-09-12
4163620823
1-495 P.036/073 F-835
:..... ~--- i.
r , .
WO 94/lOIbS PCTIUS9$/17898
poly(benzophenone sulfide- o =- ~----=-._ . _ .
o V ..., . :
phenylsulfone-sulfide) s-,f
A
polyvinyl carboxylic acid
CH-- CHZ
- = . .
C02H
. p -
trifluoro styrene
CF-CF
n
polyvinyl phosphonic acid
4_-CH.CH~
P03H2
n
polyvinyl carboacylic acid CH-CH7
I
C02H
n
polystyrene sulfonic acid
~PSSA) CH-CH2
'
n
-32-
SUBS7TTU7'E SHEET (RUI.E 26)
Sep-12-03 16:17 From-Ridout&IAaybee CA 02300934 2003-09-12
4163620823 1-485 P.037/073 F-835
WO 99/10165 pcTfus9sn7m
p~ a+ '~ , z z z z ~ c 'c c 'c -
~= S~' f- E- m F F f- F F
~ o z z z z 2
o z o
O O
t? IL
ad
" ~ c~v o o F CD
o
Cq -- ui
o 0 o c ~y ~ ... ... ..
a F+~ c'7 C' tn Z N a7 c ~*7 ~7G t0 O+ G~
r.~- \ 00 ~A in E'l~ O N] N It- I<D 14D
~
C- G% N N O
(r7 d Oe C~ G~ ~ N C N t~} CO %O u7 en
.~ ~" CO Q Q Q O C O C O O O
p.
jj_IINI~1~I I In
a
a' '~, a c ~ c -~ e-~ c~i, h N
tn tn ui
y w
O o ,a yu ~o ~c
c vi ci~
g e i~ . o Q ~.ao o - 'o~ ir W
~ ti ~~o ~a~z~aoa co
n F
.c %o Z %c o 6
E e'n i~n N ~ ~ Z
~- .... N ... e+~ ._. ... _ "" _ K
~Z 1 NN
U cflo~'oo~~~n~m~m
Iti N N 0.N -LG? O LL - is. iz~LS.=== Lz-= Gz.=, Z
-33--
SUBsTfl'ITTE SHEE't' (RULE 26)
SeP-12-03 16:18 From-RidoutM ybee CA 02300934 2003-09-12
4163620823 T-405 P.038/073 F-835
wo 99no165 PC.'T/[IS98n789s
gm~mFS OF THE INVBNTION , - -- --_._ _
The polymers described herein are cominercially available from a
variery of suppliers (unless otherwise indicated). Suppliers of these
polymers include the following: RTP, Ticona, Alpha Precision, Polynner Corp.,
,
Amoco Polymers, Greene Tweed, LNP, Victrex USA, GE Plastics, Norton
Performance, BASF, Mitsui Toatsu, Shell, Ashley, Albis, Phillips Chemical,
Sumitomo Bake, Sundyong, Ferro, Wesrlake, M.A. Hanna Eng.
The following procedures were employed in the fabrication as.id
testing of samples that were prepared in accordance with the membranes
and methods of this invention.
General Procedures
IEC PROCEDURE
1. Cut out pieces of sulfonated films (target weight 0.2g, target film
thickness 2 mils).
2. Vacuum dry films at 60 C, record dry weights and note.if fiixn.s are in
H+ or Na+ form.
3_ Boil deioriized water in separate beakers on hotplate.
4. Place films into boiling water.
S. Boil films vigorously for 1/2 hour.
6. Prepare 1.5N H2S04.
7. Place films into HzSO, and soak for 1/2 hour.
8. Remove films and rinse with deionized water.
9. Boil irn deionized water again_ Repeat until the films have soaked in
H2SO4 three times_
10. Remove films from boiling water, pat film surface with paper towel,
and rinse carefully with deionized water.
11. Place films in another beaker of water and check for pH.
12. Continue to rinse the films with water until pH is neutral to remove
any excess acid trapped in the folds of the film.
13. Prepare saturated NaC1 solution. 14. Boil the NaCl solution, pour into
screw cap vials, add fil.m and cap.
15. Place capped vials with film into water bath at 90 C for 3 hours.
16. Remove capped beaker from water bath and cool to room temperature.
- 34-
SUBSTTTUTE SHEET (RULE 26)
SeP-12-03 16:18 From-RidoutbMaybee CA 02300934 2003-09-12
4163620823 T-495 P.039/073 F-835
WO 99/10I65 P-'OUS"MM
17. Remove the films from NaCI solution by pouring the salt solution into -
another beaker (save), wash the film.s with deionized water (save aII
washings - they will be used for titration).
18. Titrate the NaC1 solution with 0.1N NaOH.
19. Take the films, pat with paper towel and take wet weight. (Use wet
weight to deternaiute water content of films.)
20. Dry the fiInes under vacuum at 60 C until constant weight.
21. Take dry weight and use this to calculate IEC_
PEROXIDE TEST PROCEDURE
22. Place film' s into the H+ form by foIIowing steps 1-12.
23. Make peroxide solution by adding 4ppm Fe to 30!o hydrogen peroxide
(28.5mg of asAmonium iron (lI) sulfate hexahydrate per liter of
peroxide obtained from Aldrich).
24. Place the peroxide solution into water bath at 68 C.
25. Add films to the peroxide solution already at 68 C.
26. Peroldde test for 8 hours and record fdm' properties (mechar,ical,
color, handling etc_).
27. if film passes, remove from peroxide, rinse with water to remove all
traces of peroxide solution.
28. Follow steps 13-21 to obtain post-peroxide test IEC.
FILM FABRICATION PROCEDURES
Film Castin
Unariented, microporous substrate fvoas can be made by dissolving
the polymer in a suitable water m.iscible solvent and casting onto a glass
plate or other surface. For example, dry PBO polymer can be dissolved in
methanesulfonic acid (MSA). The films are slowly placed into a water bath,
where solvent is rinsed frozn the films forming microporous, water-swollen
membranes of P8O polymer. Subsequent washing allows for removal of aIl
traces of the solvent_
Extrusion:
In general, the extrusion of a polymer solution (in a water miscible
solvent) faIIowed by its coagulation and washing in a water bath allows the
-35-
SUHSTiTUTE SHEET (RULE 25)
CA 02300934 2003-09-12
I
w0 99110165 Pcrivsm7sss
formation of microporous polyuier 51ms. The mechaisiical properties and
porosity are controlled by the characteristics of the polymer solution and the
details of the extrusion process.
Microporous, biaxially-oriented films of liquid crystal polymers can be
produced using a counter-rotating die (CRD) extrusion process. Solutions of
the polymer are extruded using two annular and concentric mandrels that
rotate in opposite directiarns. The rotation of the mandrels creates a
transverse shear flow that is superimposed on the axiat shear developed as
the polymer solution is extruded through the die_ The angle that the LCP
fibrils make with the longitudinal axis of the tubular extrudate is 8, where
8 can be varied from near-zero to about 60 degrees. The die rotation presets
the biaaGi.al (+9) orientation of the emerging extxudate. Subsequent post-die
blowout (radial expansion) and draw (e,-cs.nasion direction stretcb.ing) are
used to further adjust and enhance the==biaxial orientation.
The tubular exor+udate leaving the die is expanded ra.dially (blown)
with pressurized nitrogen and stretched in the machine direction by pinch
rolls to achieve the desired filna thickness. The blown and drawn PBO
bubble is imunediateiy quenched in a water bath where the film structure is
coagulated, or "locked-in-place", and the polyphosphoric acid is hydrolyzed
into phosphoric acid. The PBO film is collected under water on a spool,
which is later transferred to a fresh water storage tank where it is
thoroughly rinsed and stored in the water-swollen state until needed.
See e.g., U.S. Patent 4,963,428.
2S Solvent Exc2zan,g_e:
The water swoIIen microporous substrate is used to complete a
staged "solvent" exchange. The initial solvent (100% water) is exchanged for
the desired solvent (e.g. NMP, alcohol, etc.) in a number of stages. To
**+.nL** .~p the collapse of the pores, the exposure of the substrate flm to
the
air was mirm:~ed_ For example, note the 5 part exchange from water to
NMP as follows:
- 36 -
SuB5TiTUTE SHEET (Fflu1.E 26)
CA 02300934 2003-09-12
WO 99/10165 PCT~snwg$
START bMSB
Exchan e# 1: 100% Water 75% Water 25% NMP
E:xchan e#2: 75% Water 25% NMP 500/,Water 50% NMP
Exchan e#3: 50 /aWater 50% NMP 25% ViTater 75%NNP
F.,xchan e#4: 20% Water 80% NMP 1009/0 NMP
Exchan e#5: 100% NMP Fresh (anhvdrous) NMP
Microporous substrate films are stored in the exchanged solvent until
they are used in composite SPEM formation.
SULFONATION PROCEDURES
Sulfonation Procedure I:
Aroxnatic PES polymers can be sulfonated to conrsolled degrees of
substitution with sulfonating agents. The degree of substitution is
controlled by the choice of and mole ratio of sulfonating agent to aromatic
rings of the polymer, by the reacttion temperature and by the time of the
reaction. This procedure offers a method for carrying out sulfonation in a
heterogeneous *nan*+er, i.e., sulfonation of precipitated polymer crystals.
The polymer (preferably a polyethersulfone) is first dissolved im the
appropriate solvent (preferably methylene chloride) and then allowed to
precipitate into a fine crystalline suspension. Sulfonation is carried out by
simple admixture of the suspension with a sulfonating agent. Suitable
agen=cs include chorosulfoni.c acid and, preferably, sulfur trioadde (Allied
chemicals stabilized Sulfan BQ in CHaClz). The sulfonating agent used
should be in sufficient proportion to introduce a number of suifonate groups
onto the polymer that is within the range of between 0.4:1 to 5:1 per
polymer repeat unit, although this is not critical. The temperature at which
sulfornation takes place is cxitxcal to limiting the side reactions but varies
with the type of polymer (a preferable temperature is within the range of
from --50 to 80 C, referably -10 to +25 C).
When the desired degree of sulfonation has been reached, the
sulfonated polymer may be separated from the reaction rr- mYre by
conventional techniques such as by filtration, washing and drying.
The polymer products of the process of the invention may be
neutralized with the addition of a base, such as sodium bicarbonate, when
desired and converted to the alkali salts thereof. The alkali salts of the
-37-
SUHSTTTU'CE SHEET (RULE 26)
CA 02300934 2003-09-12
WO 99/10165 PCTJU'S98/17898
polymer products of the invention may be used for the same purposes as the
-parent acid polymers.
See e.g., U.S. Patent 4,413,106.
S Sulfonation Procedure 11:
Concentrated sulfuric acid is used as the solvent in this procedure.
The content of the sulfonating agent, sulfur trioxide, is based on the total
amaunt of pure (100% anhydrous) sulfuric acid present in the reaction
xoixture, and is kept to a value of less than 6% by weight throughout the
entire sulfonation. The sulfur trioxide may be mixed in dissolved form
(oleum, fuming sulfuric acid) with concentrated sulfuric acid. The
concentration of the starting sulfuric acid and oleum were deterniined by
measuring their density immediately before use in the reactions.
The temperature of the reactioa mixture is kept at less than +30 C
throughout the reactiort. The sulfonation procedure is stopped with the
addition of water to the reaction mixture or by pouring the reaction mixture
into water,
More specifically, the polymer is first dried in high vacuum at room..
temperature to constant weight, then tlissolved in comcentrated sulfu.ric
acid. Oleum is then added drop-wise over a period of hours with constant
cooling below +30 C, and with stirring. When all of the oleum has been
added, the reaction mixture is sstirred for a further period of hours at the
sazne temperature. The resultant viscous solution is then run into water
and the precipitated polymer is fi2tered off. The polymer is then washed
witla, water until the washings no longer are acidic, and it is then dried.
If these conditions are maintained, a controUable sulfonation of
aroraatic polyether sulfones is possible and polymer degradation can be
substastially or completely prevented.
Though less preferred, another variation of this procedure is to add
the sulfur trioxide either in pure solid state or in gaseous state to a
solution
of the polymer in concentrated sulfuric acid.
See e.g., U.S. Patent 5,013,765.
-38-
Sues-i7TUTE SHEET (RULE 26)
CA 02300934 2003-09-12
wo 99110165 rcrius98r17898
Suifonation Procedure III-
This sulfonation procedure is directly analogous to procedure I,
however, the polymer remains in solution at least until the addition of the
sulfonating agent.
Polymer is first dissolved in a solvent that is compatible with the
sulfonating agent (e.g. amethylene chloride) in a nitrogen atmosphere. The
sulfonating agent is added to this solution over the course of several hours_
The resulting solution or suspension (if the polymer precipitates as the
reaction occurs) is allowed to react, again for several hours.
When the desired degree of sulfonation has been reached, the
sulfonated polymer may be separated from the reaction mixture by
conventional techniques such as by filtration, washing and drying. If the
sulfonated polymer remains in solution, the solvent can be removed simply
by evaporation-
MEMBR.ANE PREPARATxON
Microporous substrate filrsts previously exchanged into the
appropriate solvent are placed consecutively into solutions of the various
ion-conducting polymers (ICP) with increasing concentration (in the same
solvent as the unfilled microporous substrate). This technique is lmown in
the art (see, e.g., U_S. Patent No. 5,501,831). Generally the use of smaller
changes in ICP corncentration seems to allow the formation of composite
films with higher final ICP loadings. In the case of more viscous polymer
solutions, the microporous substrates and the imbibing solution are heated
(up to 100 C). Once imbibed with the ICP, the composite ftlm is placed
between the 6" diameter tension rings_ As the rings are bolted together, the
composite is carefully stretched to eliminate any veins or defects in the
substrate. Once the rings are completely bolted together, the setup was left
to air dry (e.g- in the hood) overnight. This will usually remove much of the
excess ion-conducting polymer's solvent by evaporation.
The fi3ms are further dried by one of two methods. For low bot7ing
solvents the composite flms are heated under vacuum with pressure (about
10o psi) to prevent blistering of the films. In these instances porous,
Teflon coated shims are used to allow the solvent vapor to escape. Iiigher
boiling composite fiims are simply heated under vacuum past the
- 39 -
SUBSTiTLT[E SHEET (RULE 26)
CA 02300934 2003-09-12
wo "n016s pCrnrssan7898
atmospheric boilin.g poirtt of the solvent. The overall uziiformity of the
final
composite membrane can be improved by further pressing these composites
at elevated temperature and pressure.
COMPOSITE MEMBRANE TESTING METHODS
IEC. % water Con.terit. Thickness:
During this procedure, films are immersed in distilled HzO and boiled
for a period of 30 minutes_ The ffilms are then placed in a solution of 1.5N
H2S04 at room temperature and soaked for a period of 30 minutes. This is
repeated three separate times to ensure proper H+ ion exchange into the
mexnbrane_ Films are rinsed free of acid (pH of rinse water > S.0) and placed
into separate beakers, each filled with a saturated solution of NaCl. The salt
solution is boiled for a period of three hours. The films, which are now in
the
Na+ form, are removed from the salt solution, rinsed with distilled water and
padded to remove excess water_ Now a wet weight and thickness of the
sample are measured. VVhile in the Na+ form, the f7m.s are dried in an air
oven at a temperature of 60 C_ The dry weight and thickness of the films are
measured artd the percent water content is calculated. The salt solutions
are titrated with 0_ 1N NaOH to a phenolphthalein endpoint and IEC dry
(meq/g) values caicula.ted.
Ionic Conductivity:
Transverse ionic conductivity measurements are performed on film
samples in order to determi,ne the specific resistance (ohm"cnma). Prior to
the
ionic conductivity imeasurements, film samples are exchanged into the H+
form using the standard procedure discussed above. To measure the ionic
conductivity, the film samples are placed in a die consisting of platinum-
plated niobium plates. The sample size tested is 25cm2. Prior to assembling
in the measU.ring device, platinum black electrodes are placed on each side
of the film sample to forxn a membrane-electrode assembly (MEA). To insure
complete contact during the resistivity measurement, the MEA is
compressed at 100 to 500 psi between two platinum-plated
ni.obitun/sta.inless steel rams. The resistance of each film is deterini.ned
with
a 1000 Hz, low current (1 to 5A) bridge, four point probe resistance
measuring device and converted to conductivity by using formula 1.
-40-
SUBSTtTUTE SNEET (RULE 26)
CA 02300934 2003-09-12
Wo 99n(I2B5 PGT1US98/37895
(I)C=t/RxA)
Where: C =Conductivity (S/cm)
R =Sample Resistance (ohm)
t =Wet sample thickness (cm)
A = Sample area (cm2)
Measurements are converced to specific resistance by calculating the
ratio of thickness over conductivity (ohm*cm2).
Meznbrane Dearadation:
Accelerated degradation testing is carried out using 3% H2Oz solution
with 4 ppm Fe++ added as an accelerator_ The fiims are tested for a period of
8 hours at a temperature of 681C. The percent degradation of IEC was
measured in the film samples after the test. After 8 hours, the films are
removed froia solution, and re-exchanged using LS N H2SO4_ The IEC is
recalculated, and the test result expressed as the % loss in IEC. This test
simulates long term (several thousand hours) of actual fuel cell operation.
For H202, fuel cells, <10 /a TEC degradation in this test would be considered
acceptable.
Final Membrane Thickness / Imbibed Volume:
Once hot pressed, each composite is photographed (at the
appropriate scale) on its edge side to determine if ICP has been infiltrated
into the substrate. To get a good picture of the edge of the coia,posite, the
following procedure is used_
A srnall piece of the composite membrane is cut from the final film
and mounted, edge on epoxy. Once mounted and cured, the membrane can
be cut and polished to allow examination of the cross section by optical
macroscopy. Each coxnposite membrane is compared to a"control" substrate
which undergoes the same steps (without any ICP). This procedure allows a
determination of two important properdes: % dry loading of ICP & ICP (outet
layer) thickness.
-41-
SUBSTiTt7TE SHEET (RULE 26)
CA 02300934 2003-09-12
wo 99n0165 PCr1nls9sn7898
EXAMPLE I
Sulfonation of Radel R
Using Sulfan B (100% and 150% Sulfonation)
Sulfonation Procedure I was used in the following exarnpie.
Two separate 1000 ml 3 zzeck resin kettles (with ribs) equipped with
a.rn N2 inlet, addition funnel, and overhead stirrer were charged with the
following reactants: 340 ml of dichloromethane and 50.00 grams of Radel
R Polyethersulfosae Polymer (beads). These mixtures were stirred until
solutions formed (approximately .25 hours). Once solutions formed, they
were cooled in ice baths to about a temperature of O C (ice bath wsa
maintained throughout the duration of the addition and reaction). (Note that
Radel R was dried at 70 C under full dyrtamic vaeuum for about 12 hours
to remove any adsorbed moisture.)
Whi1e the above solutions were cooling, the following amounts of
Sulfan B were combined with dichioromethane in two separate 125 m1
addition funrlels. In funnel # 1(100% sulfonation) 10.00 grams of Sulfan B
was combined with 120 ml of diclhloromethane. In fitnnel #2 (150%
sulfonarion) 15.00 grams of Sulfan B was combined with 120 azi of
dichloromethane_
= As polymer solutions were cooled, the polymer precipitated from
solution to form a viscous paste. To each of these polymers approximately
350 ml of dichloromethane was added to aid in the uniform M+xing of the
suspemsfons. The diluted suspensions were then cooled to ice bath
temperatures once aga.in_
To the rapidly stirring cooled and diluted polymer suspension, the
Sulfan B solutions were added drop-wise over a period of 3.5 to 4.0 hours.
Upon completing the addition of the Sulfan B / dichioromethane
solution, the reaction mixtures were permitted to stir at ice bath
temperatures for another 2-5 hours, then the reaction was stopped by
adding approximately 10 ml of deionized water to each of the reaction
mixtures_
The reaction mixtures (white dispersions) were recovered by filtration
using a glass frit_ Products (white powder) were washed 3X with 100 ml
portions of dickil.oromethane_ The washed products were then permitted to
-42-
SUBS'iTtUTE SHEET (RULE 2S).
CA 02300934 2003-09-12
wo "110165 Prr/USM72s
air dry in the hood- 20% solutions of the dried products were made in NMP
and cast on soda lime glass plates. The freshl.y cast f]ms were left to stamd
in a dry box with a relative humidity of less than 5% for a period of 24
hours. The cast films were heated at 70 C under full dynamic vacuum for
a.n hour prior to floating the filras off with deionized water. The floated
films
were then permitted to air dry overnight. I
The 100% and 150% sulfomated products swell greatly in water and
become opaque, but when films are dry they shrink aad become clear once
again. The mechanieal strength of these films allows creasing while resisting
tearing. Films of the 100% and 150% products are not soluble in boiling
water, and under these conditions also maintain their mechaztical
properties.
IEC: 100% sulfonated Radel R unpurified = 1.39 meq. /g
1 S 150% suifonated Radel R unpurified = 1_58 raeq. /g
These polymers were further purified by dissolving in NMP (at
20wt_%) and then precipitated into a large excess of saturaated salt water.
The resulting polymers were soaked in sodium bicarbonate, washed several
times with water, then dried. under vacuum (-100 C). These polymers were
also cast into films as described above for eharacterization_
IEC: 100% sulfonated Radel R puzified = 1.26 raeq. / g
150% sulfonated Radel R purified = 1.44 meq. / g
Water Pick-up (wt_%):
100% sulfouated Radel ROD purified z 56%
150% sulfonated Radel R purified = 110%
EXAMPLE 2
Sulfonation of BASfi Ultrason Polyether Sulfone
Using Sulfan Bg
(85 /a, 75%, and 65% Sulfonation)
Sulfonation Procedure IlI was used in the following exa=nple.
- 43 -
SUBSTiTUTB SHEF-T (RULE 26)
CA 02300934 2003-09-12
WO 99/I0165 PCr/[JS98n789s
Three separate 1000 mI 3 neck resin kettle (with ribs) equipped with
an N2 inlet, addition funnel, and overhead stirrer were charged with the
foIiowing reactants: the first resin kettle was charged with 350 nsl of
dichlorometharne and 51.00 grarns of BASF Ultrason polyether sulfone
polymer (fine powder), the second was charged with double the amount of
reactants, and the third was charged with the same ratios as the first =
Ultrason was dried at 70 C under dynamic vacuum for about 12 hours prior
to use. These mixtures were stirred until solutions formed (approarimateiy
snin.). Once solutions formed, they were cooled in ice baths to about a
10 temperature of 0 C (ice bath was maintained throughout the duration of the
addition and reaction).
While the above solutions were cooling, the following amounts of
Sulfan B were combined wi.th dichloromethane in three separate 125 ml
additioxa funnels. In funnel # 1 (85% sulfonation) 14_94 grams of Sulfan B
15 were combined with 120 ml of dichloromethane. In addition funnel #2 (75%
sulfonation) 26.32 grams of Sulfan B were combined with. 120 ml of
dichloromethane. In addition funrlei # 3 (65% sulfonation) 11.80 grams of
Sulfan B were combined with 120 ml of dichloromethane. These solutions
were then added dropwise to the corresponding rapidly stirring cooled
polymer solutions over a period of 4 hours.
Addition of the Sulfan B solution caused the polymer to precipitate
and form a very viscous sludge. These were diluted with the following
amounts of anhydrous dichlorometlxane. Reaction # 1 was diluted with 70 m1
of anhydrous dichloroiuethane,.#2 was diluted with 600 m1 of
dichloromethane, and #3 was diluted with 400 nxt of dichloromethane_ Upon
completing the addition of the Sulfan B / dichloromethane solution, the
reaction mixture was permitted to stir and warm to room temperature
overnight. The following morning the reaction naixtures (a white dispersion)
were filtered using a glass frit. Products (a fine white powder) were washed
3X with 100 xn2. portions of dichioromethane. The washed products were
then permitted to air dry in the hood for 4 hours.
20wt.% solutions of the dried products were made in NMP. The
polymer solutions were filtered using a 2.5 micron glass fiber filter
cartridge_
The fiitered products were then precipitated into approximately 4 liters of
water. These products were then washed 2X with deionized water. The
-44-
SUHSTi'rUTE SHEET (RULE 26)
CA 02300934 2003-09-12
. ! - .~
WO 99/10165 PCT/U598/17898
washed products were converted into the sodium fornz by soaking in a 2_5%
sodium hydroxide solution over several, days. These were then washed with ~
deionized water until a neutral pH was achieved. Finally, the samples were
thorough).y dried in vacuum. = _ .
When 85% sulfonated polymer is boiled in water, it swells greatly and
partially dissolves. The 75% and 65% sulfonated products do not dissolve
in boiling water, however they show considerable swel.ling.
IEC: 65% sulfonated Ultrason purified = 0.69 meq./g
75 /a sulfonated Ultrason purified = 0.80 meq./g
85% sulfonated Ultrason purified = 1.08 meq. / g
Water Pick-up (wt.%):
65% sulfonated Ultrason purified = 18%
75% sulfonated Ultrasoa purified = 21%
EXAMPLE 3
Synthesis of Sulfonated Udel Polyether Sulfone
Using Chlorosulfonic Acid (33-100% sulfonarion)
Sulfonation Procedure III was used in the following example.
Procedure:
A 1000 ml. 3 neck round bottom flask equipped with a condenser, Nz
inlet, and overhead stirrer; was charged with 175 ml of dichloromethane and
50.0 grams of UdeT' Polyethersulfone. This mixture vvas stirred until a
solution formed (approximately 3 hours).
While the above was stirring 11.49 grams of chlorosulfonic acid was
mixed with 50 ml. of dichloromethane in a 125 ml. addition funnel. This
solution was added dropwise to the rapidly stirring polymer solution over a
period of'an hour. The reaction mixture changed from a clear amber color
to a cloudy caramel color. Upon completing the addition the acid solution,
the reaction mixture was permitted to stir at room temperature over night_
After stirring at room temperature for 28 hours the reaction mixture
was heated in a water bath until a mild reflux was achieved, and it was kept
refluxing under these conditions for an hour. After heating the reaction
-45-
SuBsT'iTUTE SHEE? (RULE 26)
_.............
_
CA 02300934 2003-09-12
-wo 99/10165 PCX7[)s9sn7848 ''
mixture for an hour the heat source was removed and the iuLxture was
perzaitted to coot_
After removal of the solvent, the product was dissolved in THF. =F'ilms
cast from this solution were transpareat and creasible. IR spectra and
water absorption were consistent with the formation of suifonated Udeil
PolyethersuZfone.
Coutplete reaction of the chlorosulfonic acid corresponds to the
addition of 0.85 sulfonate groups per repeat unit of the poIymer (85%) _
Sim7,arly, sulfonated versions of Udel:" Polyethersulfone were made with
levels of sulfonation from 33 to 100%.
IEC: 75% sulfonated Udel = 1.10 =neq_ / g
85% sulfonated Udel 1.19 meq./g
Water Pick-up (wtN:
75% su]fonated Udel 12%
85% sulfonated Ude193 /a
EXAMPLE 4
Synthesis of Sulfonated-Polyitnides
(via Monomers)
Sulfonation procedures described by Siliion [French patent
9,605,7071 were used as a guide in the following e.,cample. However,
alternate monomers and reaction conditions were emp].oyed.
Sulfonated polyimides are produced by the reaction of a sulfonated
diamine with a dianhydride, using a 1.000 molar ratio of diamine /
dianhydride, in a solvent ua.der an inert atmosphere. An exact diamine /
dianhydride xnolar ratio of 1.000 is required in order to achieve high
molecular weight polymers. Polyirnides are synthesized through an
intermediate polyaiaic acid form which contains an amide linkage and
carboxylic acid groups. This polyamic acid may or may not be isolated from
the reaction sotution. The polya.mi.c acid is converted to the corresponding
polyimide by a cyctization reaction involving the amide hydrogen and
neighboring carboxylic acid groups, forming a five (or six) membered imide
ring, with the evolution of water as a reaction byproduct.
-46-
SUBSTITUTE SHEET (RULE 26)
_------------.-..~___ _
CA 02300934 2003-09-12
wo 99/10165 PCT/US98/17898
Folyimides can be made via two general procedures: 1) first
synthesize, at or below ambient temperatures its solvent-soluble polyamic
acid form, then cheznieally or thermally transform this polyamic acid to the
polyirnide; and 2) directly synthesize the solvent-soluble polyimide using
S reaction temperatures in excess of 100 C to distill water from the initial
reaction solution. Each of these procedures was used at Foster-Miller to
produce sulfonated-polyimides. The details of these reactions are presented
below.
Formarti.on of the Sodium Salt of 2, 4 Diaminobezenesulfonfc Acid (2, 4-
NaDBS).
2,4-Diaminobenzenesulfonic acid (2,-DBS) (5.00 grams, 26.6 mmoles)
was dispersed in 95.29 gratms a.nhvdrous methanol at ambient temperatures
under a positive nitrogen atmosphere in a reaction fLask equipped with a
reflux condenser, magnetic spinbar for stuzirxg purposes and pressure
equalizing funnel. A cloudy dispersioa of sodium hydroxide (1.06 grams,
26.6 mmoles) in rnethanol (93.4 grams) at a.concentration of 1.1 wt. percent
was placed in the pressure equalizing funnel and added dropwise to the
stirring 2,4-DBS/methanol dispersion at ambient temperatures. AddiBonal
methanol (195 grams) was added to trausforna, the dispersion into a
brownish orange colored solution after stirring overnight, containing
approximately 1.3 wt. percenz solids. Initially, 2,4-DBS was found to be
insoluble at similar concentrations in metharlol, indicating 2,4-DBS has
been converted into a more soluble material. The solution was heated at
reflux for several hours to ensure the reaction had gone to completion,
cooled to ambient temperatures, and filtered to remove any trace amounts of
undissolved tnaterial. Hexanes (275 mL) were then added to the solution to
precipitate a tasinish solid. This solid was collected by filtration, washed
with hexanes and air dried. The material exhibited a single reproducible
endothermic absorption between 246 to 252 C, with a peak wddth at half
height of 5.3 C by differential scanning calorimetry. Its infrared spectrum.
(IR) showed absorptions typical for a -NH2 amine (3426, 3380, and 3333 cm
9, a primary amirte (3199em- 1), aromatic C-Hs (1624 ern- z) and SOs salt
(1230 and 1029 cm- 1) groups. These S03 salt absorptions were located at
values different than those observed for HOSOT in 2,4-DBS, which appeared
at 1302 and 1134 cm-I. The anaine absorption at 3426 cm-i in this material
-47_
SUBS'TTTUTE SHEET (RULE 26)
CA 02300934 2003-09-12
wo 99110165 Pcr11jS98n7898
was also not preseat in 2,4-DBS. The IR absorption typical for a sitlfonic
acid (-S02-OH) group at 2609 cm-i in 2,4-DBS was also absent. The
combination of all this information indicates the tannish solid product is
sodium 2,4-diamfnobenzenesuifonate (2.4-NaDBS).
This material was be used as an alternative to 2,4-DBS in rhe
synthesis of sulfonated polyimides due to its increased thermal stability and
potentially increased reactivity toward polyimide formation (amine groups in
the 2,4-NaDBS are more reactive toward the dianhydside monomer due to
electron release from the sulfonate group).
Synthesis of the Copotyam.ic Acid Derived from 6FDA, m Phenylenediamine (m-
PDA) and 2, 4-NaDBS (6FDA/ m. PDA/ 2, 4-NaDBS PAA).
2,4-DBS (7.75 mmoles) and m-PDA (7.75 mmoles) were easily
dissolved in anhydrous dimethylsulfoxide (DMSO) at ambient temperatures
under a nitrogen atraosphere. 6FDA (15.5 mmoles) was added all at once to
the diamine solution and the rnixture was stirred at ambient temperatures
under a nitrogen ataxosphere_ The reacuoa mixture became warm to the
touch as the 6FDA began to dissolve and the resulting, solution was stirred
overnight at ambient temperatures_ This clear reddish brown solutiorn
contained 15.0 wt. percent polymer and exhibited a viscosity similar to
warm syrup, indicating polymers with reasonable molecular weights had
been produced. The IR spectrum of the reactioti solution showed
absorptions typical for -NH of an anaide (3249 and 3203 cnrl), C=0 amide I
stretch (1683 cm-1), aromatic C-Hs (1607 crm l), N-C=O amide II symaxetric
stretch (1548 cm-1) and S03 salt (1256 and 1020 cm-'). The IR absorption for
-OH of HOSO2 at 2609 cm 1 was absent from the spectrum. This IR data is
consistent with the formation of the 6FDA/m-1'DA/2,4-NaDBS copolyamic
acid.
A sample of the polyamic acid solution was cast into a film on a NaC1
salt IR disc and the film/disc was heated in a cu-culating air oven for 1 hour
each at 100 , 200 and 300 C to convert the copolyamic acid to its
copolyim.ide form. The IR spectrum of copolyimide f=ilxn showed absorptions
typical for C=0 imide stretch (1787 and 1733 ccm-1), aromatic C-H (1603 cm-
1), C-N imide stretch (1362 cm-l), HOSO2 acid (1298 and 1145 cm-j), SOs salt
(1256 and 1029 cia i) and polyimide (745 and 721 cnn-1). IR absorptions
-48-
SueSY17LTrE SHEET (RULE 26)
CA 02300934 2003-09-12
WO 99II0165 PCFI[1S98n7-898 :..
typical for polvamic acids at 1683 and 1545 cnr' as well as the -OH of -
HOSO2 at 2609 cm-1 were absent_ Nevertheless, it appears that some of the
NaSOs groups were converted to HOS02 by free acid generated during the
continuing polymerization.
Thermal lrndization of 6FDA/rrt PDA/2,g-iYaDBS PAtI.
A sample of the reaction solutiozi was cast into a large film with an
initial thickness of 0.007 inch on a glass substrate using a motorized filbn
casting table located inside a low humidity chamber (< 10 percent relative
humidity). The resulting clear copolyamic acid film was heated in a
circulating air oven for 1 hour each at 100 , 200 , and 250 C to form a
xeddish brown copolyimide ftlm. A final temperature of 250 rather than
300 C was used to hopefully reduce the conversion of NaSOa groups to
HOSOz and thermal degradation of the resulting HOSOa, believed to occur
at temperatures >200 C_ The copolyimide film broke into many very small
pieces upon removal from the glass substrate, a sign that the molecular
weight of the copolyimide may be quite low.
Synthesis of the CopoIyimide Dfrectly from 6FDA, m-PDA, and 2, 4-
NaDBS (6FDAIm PDAI2, 4-NaDBS Pl) A brownish dispersion of 2,4-NaDBS
(7.47 inmoles) and rn-PDA (8-01 mmoles) in m-cresol (50 grams) and
anhydrous toluene (20 grams) in a 3-necked flask equipped with a
thermometer, mechanical stirrer, and Dean Stark trap I'a.tted with a
condenser/nitrogen inlet was heated at about 150 C under a nitrogen
atmosphere. 6FDA (15.49 mmoles) was added to the hot dispersion,
whereupon water imxnediately began to distill out of the reaction dispersion
and become collected in the trap. The temperature of the brownish
dispersion was gradually increased to about 200 C, maintained at 200 C for
7.5 hours, and then decseased to ambient temperatures. The resulting dark
brown colored, viscous reaction mixture was found to be a dispersion
contJaitiing sigaificant quantities of crystalline material(s). The IR
spectrum
of the reaction dispersion showed absorptions typical for or C-0 imide
stretch (1781 and 1723 caxz-1), C-N imide stretch (1365 cm-1), SOs salt (1251
and 1033 cm-t), and polyimide (738 and 720 cm-1). The presence of m-cresol
in the film prevents determination of whether HOSOz groups are present
due to overlapping absorptions. IR absorptions typical for polyamic acids at
-49-
Su6S'RTU'fE SHEET (RUI..rm 26)
- ------------------
CA 02300934 2003-09-12
' ! l
WO 9sno16s pCT/ElssB/173ss
1683 and 1548 cm= 1 as well as the OH stretch of HOSOz were absent. IR
data indicated some sodiurn sulfonate-copolyimide had been produced = -
under the reactiorx conditions, but the presence of a crystalline dispersion
rather than solution suggests a significant amount of the diamine was not
incorporated into a polymer.
The consistent problem encountered during these reactions was low
molecular weight of the fix~.~ product. The above syntheses did not provide
a creasable, sulfonated polymer film. However, fragments of the polymer are
unchanged by the peroxide test and have IECs up to 1.13 meq./g.
It is anticipated that higher molecular weight poiymer will be
obtained by further purifying the 2,4-NaDBS monomer prior to
polymerization. In addition, the use of isoquinoline as a polymerization
catalyst may accelerate the reaction.
1S EXA,MPLE 5
Sulfonation of Victrex Poly(Ether Ketone)
Using HzSOo / SOs
Sulfonation Procedure II was used in the following exarapie.
Pr~=
30.00 g PEK polymer was dissolved in 270g of concentrated sulfuric
acid (93.5wt.%) under ri.itrogen, stirred by an overhead mechanical stirrer.
The polymer was dispersed over several days to form a dark red thick
solution.
176g of this solution was left in the three neck flask with overhead
stirrer, N2, etc. To the flask, 208.4g of fuming sulfuric acid (25.5wt. % free
S03) was added over the coarse of a few minutes with constant stiirirtg to
raise the solution to a free SO3 content of 2wt. %. The resulting solution
was immersed in a room temperature water bath to control the temperature.
Samples were removed after approx. 1 hour, 3 hours, and 16 hours,
and quenched into deionized water to precipitate.
In order to make films, the 1 and 3 hour products were washed
several times with deionized water, soaked overnight in approximately O.SM
NaOH solution, then washed until a neutral pH was achieved. These were
blotted dry and placed in the vacuum oven overnight at 50 C. Dried
-50-
SUBSTtTtJTE SHEhT (RMS 26)
CA 02300934 2003-09-12
WO 99/10165 PCr/US9147398
samples were dissolved in NMP to make a 20wt. % solution. This required
heating overnight at 60 C. Filtns of approx. 6 mils were cast onto a freshly
cleaned glass plate. After two days of drying the Sims were removed by -
iznmersion into deionized water.
Soaking the films in water (at room temperature) caused considerable
swelling to give a hazy gel-like consistency, but did not dissolve. Films cast
from the 1 hour and 3 hour samples did not dissolve in water. Film of the I
hour product could be hydrated and dehydrated, while maintaining
resistance to tearing. The 1 hour sulfonated PEK film IEC was measured to
be 2.3m,eqJg_
EXP,.MPLE 6
Sulfonation of PPS/SO2Using 97.5 % H2SO4
Sulfonation Procedure II was used in the following example.
PPS / S02 provided by James McGrath of VPI (see Svnthesis and
Characterizatiozz of Poly(Phenylene sulfide - sulfos.ie). Polymer Preprints 38
(1), 1997, p.109- 1121.
Procedure=
.-
250 m13 neck round bottom flask was equipped with an overhead
stirrer, N2 inlet, and addition funnel were charged with 100 grams of 93_5%
sulfuric acid- To the rapidly stirring sulfuric acid 25.00 grams of the'
PPS/SO2 was added. The mixture was stirred at room temperature until a
solution formed (approximately 1 hovr).
When solution laad formed the temperature was lowered to about 0 C,
and 60.0 grams of 23.0% fitmzing sulfuric acid was added dropwise over a
period of a 0.5 hours.
Ice bath temperatures were maintained for the first 3.5 hours of the
reaction. Aliquots were taken at T=0.5, 1.5, 2.0, and 3.0 hours by
precipitation the reaction naixtures were precipitated into deionized water.
Precipitated product appeared not to have swo3len to any appreciable exteut,
so the rexnaining reaction rnixture was warmed to room temperature.
Aliquots were taken at t=3:30, 4:30, 7:00, and 8:20 (approximately 4 hours
at room temperature) _
-51-
SUHST7TL,1TE SHEET (RULE 26)
CA 02300934 2003-09-12
l
wo "n0165 Pc'Nsmn9s "
Products were rinsed 3 times with deionized water. soaked in
saturated sodium bicarbonate solution until basic and then washed in
deionized water vntii neutral.
Solubilizing of the sulfonated PPS/SO2 polymers was attem.pted after
drying the precipitated polymer at 100 C for 3 hours under full dynamic
vacuum. The polymer solutions were inade with fresh anhydrous NMP and
were immediately cast on soda lime glass plates at a thiclaness of 2 mils_ The
freshly cast films were placed in a level oven preheated to 100 C aud dried
under full dynamic vacuum for 1 hour- After drying (at 100 C) for an hour,
the oven temperature was raxsed graduaIly to 200 C over a period of 3
hours. When the 200 C was achieved, the oven was shut off and the films
were permitted to gradually cool to room temperature. Films were removed
from the glass plates by floating them in deionized water.
Based on crude observations of the PPS/SOz fiLms, this material
appears not to have sulfoxsated to any appreciable extent while kept at 0 C
(little dimensional changes were observed on boiling in water). The PPS/SOz
samples that were reacted at room temperature appear to show some sigas
of sulfonation (swelling and taking on a rubbery appearance in boiling
water).
IEC sulfonated PPS / SO2:
T-8:20, 0.53 tneq./g
Water Pick-up (wt_ /a) sulfonated PPS/S02:
T=8:20, 15%
IEC's of the sulfonated PPS/SO2 samples were appreciable but
further sulfonauon should be possible with increased reaction times.
EXAMl'LE7
Sulfonation of Poly(phenylquinolxaline) Film
This procedure has been used for the sulfonation of PBI and PPQ
fiiins. See e.g., U.S. Patent No. 4,634,530 and in L.inkous, et al., J. Polym-
Sci., VoI. 86: 1197-1199 (1998).
-52-
SU6STITUTE SHEFI' (RULE 26)
CA 02300934 2003-09-12
wo 9sno165 PC PrtTS9sra7s9s
The film is soaked in a S0Q/o solution of HzSO., for a.pprox. 2 hour in
order to fully sulfate it; then baked at a min+-um temperature of 300 C to
cosxvert the anunotlium sulfate salt to the covalently bonded sulfonic acid.
EXAMPLE 8
Fabrication of SPEM
Using PBO and sulfonated Radel RO
Ion-conducting membranes were fabricated from the polymer
substrate fil.m PBO and various sulfonated poly(ether sulfones). The
substrate utilized was PBO f.ilm exvruded and solvent exchanged into NMP
as described above in the general procedure. The ion-conducting polymer
(100, 150% sulfonated Radel ROD - Na+ fortn) was synthesized according to
ex.3mple 1 given above.
Microporous PBO, having been exchanged into NMP without coIlapse
of the pores, was added to a Swt.% solution of the sulfonated Radel R
polymers in NMP. After twelve or more hours, the films were removed and
placed in a 20wt.% solution of the same ion-conducting polymer (also in
NMP). After twelve or more hours at room temperature (or at 75 C) the films
were removed, stretched in tensioning rings, and dried of the solvent (see
general procedure outliaed above). Specifi.cally, the sulfonated Radel R /
PBO film' s were dried in a low humidity chamber (<59~'o RH) for 1 to 2 days,
vacuum dried in an oveni, heated from below 60 C to about 200 C.
After all solvent is fully extracted from the membrane, the composite
is preferably hot pressed. The hot pressing operation facilitates ilow of the
ion-conductor to make a homogenous composite structure. Non-porous
Tefton shims were placed on each side of the composite membr=e
followed by Titanium shi.m.s. The entire setup is then loaded into a press
and subjected to the following cycle:
High Temperatv.re Hot Press
Step Temp. Hold Time Force Rannp Rate
1 392 F 5 mi,n 1.0 klb 15 F/miu
2 392 F 15 mi.n 28.3 klb N/A
3 392 F 5 min 28.3 klb 25 F/min
-53-
SUBSTiTUTE SHEET (RUI.B 26)
CA 02300934 2003-09-12
wo "119I65 PcrRS"1178ss
Note that the 28.3 kibf corresponds to a press pressure of 1000 psi.
SPEMs produced via this example were FMI 126-17P, F1VII 126-17Q,
FMI 126-17T, FMI 126-17U. See Table 8 for various results obtained from
SPEMs made via this procedure.
EXAMPLE 9
Fabrication of SPEM
Using PBO and sulfonated Udel 4D
Ion-conducting membranes fabtica.ted in this example followed
closely those in example 8.
The substrate utilized was PBO film extruded and solvent exchanged
into THF as described above in the general procedure, The ion-conducting
polyraer (75, 85,100% sulfonated Udel) was synthesized according to
example 3 given above.
For composite SPEMs of 100% sutl.fonated Udel ion-conducting
polymer, miCroporous PBO fiiaxs exchanged into THF were placed into
30wt. /a solutions of the polymer (in THF) at room temperature. After more
than twelve hours, the films were stretched irn tensioning rings and allowed
to dry in a low humidity chamber. Final traces of the solvent were removed
with the following vacuum pressing shown below.
Low Texnpetature Vacuum Pressio.g
Step Temp. Hold Time Force Ramp Rate
1 122 F 20 rain 2.9 klb I S F/msn
2 167 F 20 min 2.9 kIb 15 F/min
3 212 F 20 min 2.9 klb 15 F/mi.a
4 257 F 20 min 2.9 klb 15 F/min
5 85 F 5 min 2.9 k1b 25 F/min
The force of 2.9 klb corresponds to a press pressure of 100 psi. Films were
finaUy hot pressed without vacuum io fuIly consolidate the composite
structure, as shown below.
-5a--
SUBSTITUTE SHEhT (RULE 26)
CA 02300934 2003-09-12
WO 99n0165 Pcrl[rs9sn789s
High Temperature Hot Press
Step Temp. Sold Time Fozee ' Ramp Rate
1 317 F 30 min 28.3 ktb 15 F/man
2 85 F ----- 28.3 klb 25 F/min
The force of 28.3 klb corresponds to a press pressure of 1'000 psi_
Composite SPEMs were made with both 75 and 85% sulfonated Udel
ion-conducting polymers.
SPEMs produced via this example were FMI 539-22-1, FMI 539-22-2,
FMI 539-22-3. See Table 8 for various results obtained from, SPEMs made
via this procedure.
EXAMPLE 10
Fabrication of SPEM
Using Solubilized Nafion 1100 EW
Ion-conducting membranes fabricated in this e.+cample followed
closely those in example S. The substrate utilized was PBO esrsvuded film and
solvent excha.nged
into a mixture of water and alcohols (see below) as described above in the
general proceduxe. The ion-conducting polymer used was solubili2ed
Nafion 1100 EW purchased from Solution Technologies ( I Owt.% in a
mixture of water and propanols). The solvent system used to exchange the
PBO fitms was made to approximate that of the Nafiozi soiution.
Composite membranes were made by placing the exchanged films
directly into the lOwt.% Nafion solutions. After twelve or more hours,
these were removed and stretched into tensioning rings as described above.
These films were dried in a low humidity chamber for at least 24 hours.
Removal of the final traces of solvent were done by placiug porous PTFE
shims on each side of the composite membrane followed by the Titanium
shims. This setup was thezi loaded into a vacuum press and subjected to
the following cycle:
-55-
SUBSTCCUTE SHEET (RULE 26)
CA 02300934 2003-09-12
WO 99/I0I65 pCTMS9M7M
Low Texaperature Vacuum Pressing -
Step Temp. Soid Time Force Ramp Rate
1 125 F 20 min 2.91t1b 16 F/min
2 170 F 20 rzun 2.9 klb i5 F/min- 3 215 F 20 min 2.9 kib 15 F/min
4 274 F 20 min 2.9 klb 15 F/min
85 F 5 min 2.9 kIb 25 F/anin
The force of 2.9 klb corresponds to a press pressure of 100 psi. Films were
final.ly hot pressed without vacuum to fully consolidate the composite
5 structure, as showxz below.
High Teanperature Hot Press
Step Temp. Hold Tizne Foroe Ramp Rate
1 275 F 5 min 1.0 kib I5 F/min
2 27S F 15 uiirn 28.3 klb N/A
3 85 F 5 min 28.31cib 25 F/min
The force of 28.3 lslb corresponds to a press pressure of 1000 psi.
SPEMs produced via this example were FMI 126-16N, FMI 126-160.
See Table 8 for various results obtained from these SPEMs. The low IECs
obtaiaed from these films and the correspondingly high resistances are a
function of the low loading of ion-conductor in the composite structure. It is
anticipated that using more concentrated solutions of the ion-conductor in
imbibing the substrate will lead to composite SPEMs of low enough
resistances for the applications described. The stability of the lateral
dimensions of these Nafi.on based composite membranes presents a
significant improveznent over unsupported Nafion 117 films (which show in
plane dimensional changes on hydration of about 20 0). Given the
excerptional strength of the PBO substrate, the mechanical properties of the
composites wiII be well in excess of current state of the art fuei ceu
membranes.
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SU6STiTUTE SHEET (RULE 26)
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wo 9sn016s rc.-riUS9s117898
EXAM.PLE 11
Fabrication of SPEM
Using PBO and sulfonated tTitrason~'s
Ion-conducting membranes fabricated in this example followed
closely those in example S. The substrate utilized was PBO film extruded
and solvent exchanged into NMP as described above in the general
procedure. The ion-conducting polymer (75% sulfonated Ultrason purifed -
Na+ form) was syathesiaed according to example 2 given above.
Microporous PBO, having been exchanged into NMP without collapse
of the pores, was added to a solution of the suifonated 75% sulfonated
Ultrason polymer in NMP (8 or 12 wt.%). After twelve or more hours at room
temperature the filxns were removed, stretched in tensioning rings, axid
dried of the solvent (see general procedure outlined above). Specifically, the
sulfonated Radel R / PBO films were dried in a loiar hum.idity chamber
(<5% RH) for 1 to 2 days, vacuum dried in an oven heated from below 60 C
to 140 C.
Low Temperature Vacuum Pressing
Step Tesap. Hold Time Force Ramp Rate
1 125 F 20 min 2.9 lcib 15 F/aLin
2 200 F 20 min 2.9 klb 15 F/min
3 275 F 20 min 2.9 lklb 15 F/u3in
4 390 F 20 n-An 2.9 klb 15 F/min
5 85 F ------ 2.9 klb 25 F/min
The force of 2.9 kIb corresponds to a press pressure of 100 psi. Films were
finally hot pressed without vacuum to fu]ly consolidate the composite
structure, as shown below.
After all solvent is fully extracted from the membrane, the composite
is preferably hot pressed. The hot pressing operation facilitates flow of the
ion-conductor to make a homogenous composite structure. Non-porous
Teflon shims were placed on each side of the composite m.embrane
followed by Titanium shims. The entire setup is then loaded into a press
and subjected to the following cycle:
-57-
SUBSTiTUTE SHEET (RUl.E 26)
CA 02300934 2003-09-12
... (f wo 99n0165 pci
High Temperature Hot Press-""-
, -... .. -
Step Temp. Hold Time Force Ramp Rate
1 390 F 15 aun 28.3 klb -15 F/m.ia
2 85 F 5 rnirn 28.3 Iklb 25 F/min -
Note that the 28.3 klbf corresponds to a press pressure of 1000 psi.
SPEMs produced via this example were FMI 126-08E, FMI 126-08F_
See Table 8 for various results obtained from SPEMs made via this
procedure.
-58-
SUBSTiTUTE SHEET (RULE 26)
-~.---,-_,_.~__ ........ . ... .
