Note: Descriptions are shown in the official language in which they were submitted.
1263796
--1--
This application is a division of Applicatisn No.
514,060, filed July 17, lg86.
The present invention relates to a process for preparing
silicon-containing preceramic po]ymers useful for making
silicon carbide and silicon nitride/silicon carbide ceramics and
for their pyrolysis to such ceramic materials.
There is a great deal of interest in preceramic polymer
materials, which can be pyrolyzed to yield silicon carbide,
silicon nitride and other silicon-based ceramic materials. R.W.
Rlce, Amer Ceram. Soc. ~ull., 62: 889-892 (1983). Applications
for such polymers include, among others:
1. formation into complex shapes and subsequent pyrolysis
to give a ceramic material of the same shape;
2. spinning into continuous fibers whose subsequent
pyrolysis yields ceramic fibers;
3. as a matrix material for carbon or ceramic fibers, or as
a binder for ceramic powders ~with subsequent pyrolysis to form
a ceramic body);
4. oxidation-resistant coatings on otherwise oxidizable
materials (such as carbon/carbon composites) - after the polymer
coating is made, it can be pyrolyzed to give the resistant
ceramic coating;
5. infiltration of porous ceramic bodies such as ones
obtained from reaction-sintered silicon nitride by the polymer
itself (if liquid) or by a solution of the polymer, with
subsequent pyrolysis to form a ceramic, resulting in better
strength, oxidation resistance, etc., of the body; and
6. formation of thin films of the ceramic material for
electronics applications.
~63~9~
-2-
For instance, Penn et al., J. APD1 ~ PO1Vmer SCi . 27 :
3751-61 (1982) describe the preparation oE silicon
carbide-silicon nitride fibers from a polycarbosilazane
precursor. Tris(N-methylamino) methylsilane monomer was formed
by reaction of monomethylamine and methyltrichlorosilane in dry
petroleum ether and a polycarbosilazane resin was formed by
passiing the monomer over glass Raschig rings at 520C. The
brittle polymer was soluble ln methylene cllloride nnd
chloroform, etc. This product was spun into fibers, crosslinked
in air and then pyrolyzed to give ceramic fibers.
Other polymer precursors for forming silicon carbide and
silicon nitride ceramics have been described in ~.S. Pat. Nos.
3,108,985; 3,853,567; 3,892,583; 4,310,651 and ~1,312,970. These
linear or crosslinked polymers and processes for producing
ceramic materials have generally been found to be deficient in
one or more ways.
S. Yajima, mer, Cer~m. Soc, ~ull,, 62: 893-898; 903 (1983)
discloses using (CH3)2SiClz as a starting material Eor a
preceramic polymer for the preparation of SiC-containing
ceramics. The polymer of Yajima is prepared by sodium metal
condensation of (CH3)2SiC12 to result in a polysilane,
-[(CH3)2Si]n- (n is approximately 30). This polysilane
can then form either a "Mark I" polymer or a "Mark III" polymer
depending upon the treatment used. Heating in an autoclave
under argon at 100 kPa at 450-470C for 14 hours results in
a Mark I polymer while adding a few percent of a
polyborodiphenylsiloxane and heating under nitrogen at ambient
pressure at 350C for 10 hours results in the Mark III
polymer. In either case, the poly-silicon backbone is converted
to a polymeric chain in which the main repeat unit is:
'11 263796
--3--
~H3
-[~li~Cll2]~ (I)
H
The Mark I polymer also contains some -[(C}l3)2SiCH2]-
units. The Mark III polymer contains some Si-Si bonds in the
form -[(CH3)2Si-Sl(C~l3)2]n((n=2-8) units and a low
percentage of [(C6H5)2SiO] units These preceramic
polymers can be processed to give ceramic fibers containing SiC,
some free carbon and some SiO2. However, there are problems
associated with these polycarbosilane-derived
ceramics. They have a tendency to crystalli~e below 1200C,
they have a detrimental SiO2 content as a result of an
oxidative cure step, and free carbon and a relatively low
ceramic yield is obtained upon their pyrolysis for a commercial
product. While the ceramic yield for the Mark III polymer is
68%t the yield for the Mark I polymer is only 54%.
It would be useful to have a polymer precursor that is
formed from readily available and relatively cheap starting
materials, that is stable at room temperature, is soluble in
organic solvents and whose pyrolysis can typically provide a
high yield of ceramic products. It would also be useful to be
be able to form a ceramic material upon pyrolysis which contains
substantially no fr0e silicon, carbon or SiO2.
SummarY of Invention
We have now found that reaction of a metal amide with an
organosilicon polymer containing Si-H repeat units yields new
polymeric organosilicon compounds which are useful preceramic
materials. Upon pyrolysis these typically give ceramic yields
significantly better than the original polysiloxane compound.
Preferably, the metal amide is a polymeric alkali metal
silylamide of the formula
~63796
--4--
[(RlSiHNtl)a(RlSiN)b(RlSiHNM)c]m (where a + b + c ~
l); Rl is a lower alkyl group having from 1 to about 6 carbon
atoms, a substituted or unsubstituted cycloalkyl group having
from 3 to about 6 carbon atoms, a substituted or unsubstituted
lower alkenyl group having from 2 to about 6 carbon atoms, a
substituted or unsubstituted lower aryl group having from 6 to
about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl
group or a di(lower)alkylamino group; M is an alkali metal or
one-half equivalent of an alkaline earth metal; and m is an
integer greater than 1). This alkali metal poly(silylamide) may
be preformed and added to the Si-H containing organosilicon
polymer. Alternativelyj one may prepare the alkali metal
silylamide in situ, in the presence of the organosilicon
compound.
Preferably the organosilicon polymer is a polysilane
compound of the formula [(RSiH)X(RSi)y]n, (where x + y -
1, n is an integer greater than 1, R is a lower alkyl group
having from 1 to about 6 carbon atoms, a lower alkenyl group
having from 2 to about 6 carbon atoms, a substituted or
unsubstituted lower aryl group having from 6 to about 10 carbon
atoms, or a tri(lower)alkyl- or di(lower)alkylsilyl group), or a
polycarbosilane polymer containing repeat units of the formula
[RaSi(H)-(CH2)q],i.e.,
Rla
-lsi-(cH2)q- (II)
(where q is an integer 1 or greater, Ra is H, a lower alkyl
group having from 1 to about 6 carbon atoms, a cycloalkyl group
having from 3 to about 6 carbon atoms, or a substituted or
unsubstituted lower aryl group having from 6 to about 10 carbon
atoms).
The present invention is more especially concerned
with the aforementioned polycarbosilanes.
~263796
--5--
Aryl-substituted polymers of the type
~RaSi(}l)-(Cll2)q], and [RSill]n (e.g., where R, or Ra is
phenyl), react in the same way as the above described
polycarbosilanes and organopolysllanes to give new
polycarbosllane/organopolysilazane,
organopolysilane/organopolysilazane and hybrid polymers,
respectively.
In one embodiment of the present invention, the polymeric
alkali metal silylamide is generated by treating the ammonolysis
product of RlSiHX2 (Rl is as derined above and X is a
halogen) with a basic catalyst capable of deprot~nating the
hydrogen from a nitrogen atom adjacent to a silicon atom. The
silylamide thus formed can react with the organosilicon
compound, for example, the [RaSi(ll)-(CH2)q] already
present. With either the preEormed polysilylamide or the in
situ silylamide procedure, the reaction mixture containing the
organosllicon polymer having Si-l~ repeat units and the
polysilylamide i9 stirred at room temperature and preferably
heated at reflux in a suitable solvent such as tetrahydrofuran
to complete the reaction. The resulting solution is then coolsd
and quenched with an organic halide or a silicon halide to
produce the preceramic organosilicon polymers of the present
invention. The polymers formed by either method can then be
pyrolyzed to yield ceramic materials in high yield.
Brief Description of Drawings
Figure 1 is a proton N~R spectrum comparing a polymer formed
by adding already preformed polysilylamide (III-37~ with a 1:1
by weight physical mixture of polycarbosilane and preformed
polysilylamde.
Figure 2 is a proton N~R spectrum comparing a polymer formed
by adding already preformed polysilylamide (III-7) with a
polymer formed with polysilylamide generated in situ (III-42).
~63796
--6
Figure 3 is a thermogravimetric analysis (TG~) curve of
polymer III-7.
Figure 4 is a TGA curve of polymer III-42.
Detailed DescriPtion Or the Invention
We have discovered that the reaction of a metal amide with
an organosilicon polymer containing Si-H repeat units (referred
to as an Si-H containing organosilicon polymer) results in novel
preceramic polymers. Most preferably, the metal amide is a
polymeric alkali metal silylamide oE the f~mula
[(RlSiHNH)a(RlSiN)b(RlSiHNM)C]m (where a ~ b ~ c -
l; Rl is a lower alXyl group having from 1 to about 6 carbon
atoms, a substituted or unsubstituted cycloalkyl group having
from 3 to about 6 carbon atoms, a substituted or unsubstituted
lower alkenyl group having from 2 to about 6 carbon atoms, a
i~ , substituted or unsubstituted lower aryl group having Erom 6 to
about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl
group or a di(lower)alkylamino group; M is an alkali metal or
one-half equivalent of an alkaline earth metal; and m is an
integer greater than 1). However, as will be discussed below
other metal amides can be used in the present invention.
The Si-H containing organosilicon polymer is preferably a
polysilane compound of the formula [(RSi~l)x(RSi)y]nl
(where x ~ y - 1, n is an integer greater than 1, R is a lower
alkyl group havlng from 1 to about G carbon atoms, ~ lower
alkenyl group having from 2 to about 6 carbon atoms, a
substituted or unsubstituted lower aryl group having from 6 to
about 10 carbon atoms, or a tri(lower)alkyl- or
di(lower)alkylsilyl group), or a polycarbosilane polymer
containing repeat units of the formula
[RaSi(H)-(CH2~q],i.e.,
~2~i37~6
--7--
Ra
~$i~(CH2)q~ (II)
H
(where q is an integer 1 or greater, Ra is H, a lower alkyl
group having from 1 to about 6 carbon atoms, a cycloalkyl group
having from 3 to about 6 carbon atoms, or a substituted or
unsubstituted lower aryl group having from 6 to about 10 carbon
atoms).
In accord with the present invention, treatment of, Eor
example, organopolysilaries witll an alka~i metal amide will
provide higher molecular weight preceramic materials and improve
the ceramic yield. Preferably, one uses organic alkali metal
amides for treating the organopolysilane. Organic alkali metal
amides are well known to the person of ordinary skill in the
art. Examples include: potassium piperidide, ~ K,
potassium ethylamide, C2H5NIIK, and potassium
diisopropylamide, (i-C3H~)2NK, corresponding lithium,
sodiuin, rubidium and cesium derivatives and the like. Polymeric
secondary ~mines may be partially deprotonated by a strong base
to give polymers containing metal amide functions. Such
products also may be used to react with
[(CH3SiH)X(CH3Si)y in this invention. Examples of such
polymeric amines are: poly(ethyleneimine), [CH2CH2NH]n, or
Ciba-Geigy ChimassorbTM94~ polymer,
L N ~ CH2)6 ~ N ~ N
,~ ~ P~ l . P~ ~j/
The reaction of CH3SiHC12 with an alkali metal will
produce methylsilicon compounds of the formula
~Z63796
--8--
[(CH3SiH)X(CH3Si)y]n, where x + y = l; and n is an
integer greater than 1 (hereinafter such compounds will be
reEerred to as "methylpolysilanes"). The ceramic product
obtained when this compound is pyrolyzed contains an excess of
"Eree" silicon, rather than the ideal lSi:lC composition.
Further, depending upon the particular process used to obtain
the methylpolysilane, other deficiencies can arise. A ceramic
yield of less than 50% after pyrolysis typically represents an
unacceptable preceramic polymer. Of the above described
methylpolysilanes, those with xay which on pyrolysis gave a
reasonable ceramic yield, had only a limited solubility in
organic solvents, thus limiting further processing.
Additionally, conversion of these polymers to ceramic fibers
appears to require a photolysis-oxidation cure step. A
methylpolysilane of the above-described formula, in which the
crosslinking of the product is not as excessive (x>y) and, which
is, therefore, more soluble in organic solvents, on the o~her
hand provides an unacceptably low ceramic yield on pyrolysis,
e.g., 12-27% in various runs. Consequently, alkali metal
condensation of CH3SiHC12 does not give a very useful
preceramic polymer which can be used to form SiC and other Si/C
ceramic materials.
After extensive research we have now found that
or.ganopolysilnnes such as the methylpolysilnnes ol~tnined in the
above reactions, upon treatment with catalytic quantities of
alkali metal amides in accord with the present invention, yield
preceramic polymers of higher molecular weight which upon
pyrolysis give significantly higher ceramic yields. Such
polymers, when prepared as described herein, are soluble in
organic solvents.
The resulting products obtained when the organic alkali metal
amides were used with the methylpolysilanes were white solids
~ Z63796
g
with a higher molecular weight than the starting material. The
ceramic yields obtained on pyrolysis to 1000C typically are 50
to 60%, or more
More l~reEernbly, one utilizes nn nlkaLi metnl. si].yl~mide.
Common alkali metal silylamides that can be used in the practice
of the present invention include: [R2R3R4Si]2NM wherein
R2, R3 and R4 are each a lower alkyl group having from 1
to about 6 carbon atoms, a lower alkoxy group having from 1 to
about 6 carbon atoms, a substituted or unsubstitut:ed vinyl
group, a suhstituted or unsubstituted allyl group, a substltuted
or unsubstituted lower aryl group havlng from 6 to about 10
carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or
a di(lower)alkylamino group, R2, R3 and R4 may be the same
or diffarent; and ~ is an alkali metal or one-half equivalent of
an alkaline earth metal. Common alkali metal silylamides
include: [(CH3)3Si]2NK, i(CH3)2(CH2-CH)si]2NK~
The alkali metal silylamide can also be partially deprotonated
cyclo-[R5R6SiNH]m containing ~R5R6SiNM] units wherein
R5 and R6 are each a lower alkyl group having from 1 to
about 6 carbon atoms, a lower alkoxy group having from 1 to
about 6 carbon atoms, a substituted or unsubstituted vinyl
group, a substituted or unsubstituted allyl group, a substituted
or unsubstituted lower aryl group having from 6 to about 10
carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or
a di(lower)alkylamino group, R5 and R6 may be the same or
different; M is as defined above and m is an integer greater
than 1. For example, the reaction products of one molar
equivalent of KH with one of cyclo-[(CH3)2SiNH]3 or of one
molar equivalent of KH with one of
cyclo-~(CH3)(CH2 CH)SiNH]3, and the like. The person
skilled in the art can select other alkali metal silylamides to
use, including the lithium, sodium, rubidium and cesium
derivatives. Treatment of either the organoploysilane or the
. .
-
~Z63~796
-10-
polycarbosilane with the alkali metal silylamides generally
increases the ceramic yield in the pyrolysis of the resulting
preceramic polymer.
Polycarbosllane polymers that are used in the prcsent
invention preferably contain a multiplicity of repeat units of
the formula [RaSl(}l)-(C112)q] (where q and Ra are as
defined above)(hereinafter polymers containing such repeat units
are referred to as "polycarbosilanes"). The reaction oE these
polycarbosilanes with an alkall metal silylamide results in
novel preceramlc polymers. Typlcally, the pyrolysls of thls new
polymer glves a black ceramlc solid in a yield that is about 10
to 50% greater than the parent polycarbosilane.
Tl~e polycarbosllane polymer should contnin n~ lenst 25 mole
% of repeat unlts of the formula II, l.e. ~RaSl(H)-(CH2)q],
ln addition to other repeat units, such as [Ra2Si(C112)q]
(e.g. the Ya;ima polymers). Preferably the polycarbosilane
polymer contains at least 35 mole ~ of repeat units of formula
II. More preferably, the polymer contains at least 50 mole
repeat units of formula II.
The polymer may also contain a mixture of repeat units of
the above described formula, e.g., both [RaSi(H)~(CH2)q]
and Ra'Si(H)~(CH2)q'] (Ra' and q' are defined the same
as Ra and q, respectively, but Ra' may be difEerent than
Ra and q'may be different than q). Ra is preEerably a lower
alkyl group, more preferably Ra is CH3. Preferably q is
equal to 1 - 3, more preferably it is equal to one.
The polycarbosilane and alkali metal silylamide are
typically added in a weight ratio of polycarbosllane: alkall
metal sllylamide of about 10:1 or less. Preferably this ratio
is about 5:1 or less. More preferably the ratio is about 3:1 or
less. Most preferably the ratio is about 1:1.
Preferably the polymeric silylamide used has the formula
~Z637~6
~(RlSiHNII)a(RlSiN)b(RlSiHNM)c]m. These
polysilylamide compounds have been described in U.S.
Patent 4,482,669, issued November 13, 1984.
R preferably is a ~ower alkyl group,
more preferably CH3. This patent describes the formation of
novel preceramic polysilazanes by treatment of the mainly cyclic
ammonolysis product of, for example, CH3SiHC12 with
catalytic quantities of a base, for example, KH in organic
solvents, for example, tetrahydrofuran, THF. After these
compounds are treated with an electrophile such as methyl
iodide, CH3I, polymers having the general formula
[(cH3siHNH~a(cH3si)b(cH3siHNcH3)c]m are
obtained. Prior to the addition of CH3I, a reactive "living"
polymer intermediate, an alkali metal silylamide of the type
[(CH3SiHNH)a(CH3SiN)b(CH3SiHNM)C]m is obtained
This intermediate species can react with electrophiles other
than CH3I, e.g , with diverse chlorosiianes. Pyrolysis of
such CH3I-treated polysilazanes typically yields a ceramic
material contalning SiC, Si3N4 and "free" carbon.
The use of the polymeric alkali metal silylamide of the
l ~(RlSiHNH) (RlSiN)b(R SiHNM)C]m in
embodiment of the present invention upgrades the Si-H containing
organosilicon polymer, for example, the organopolysilanes and
the polycarbosilanes to new polymers which give a high ceramic
yield on pyrolysis. When this alkaii metal silylamide,
[(RlSiHNH)a(RlSiN)b(RlSiHN~)C]m, is reacted with
an Si-H containing organosilicon polymer, the reaction product
after treatment with a suitable electrophile such as an organic
or a silyl halide, incorporates both starting materials. When
this reaction product is pyrolyzed, the ceramic yield is
significantly greater than that of the "parent" organosili~on
polymer.
12~3796
-12-
The weight ratio of Si-iI containing polymer to alkali metal
silylamide can vary widely. For example, mole ratios of
organopolysilane: polymeric alkali metal silylamlde Erom about
4:1 to about 1:4, and preferably from 2.5:1 to 1:2 typically
provide useful results. Weight ratios of polycarbosilane:
polymeric alkali metal silylamide from about lO to about l; and
preferably from 5:1 to 1:1 typically provide useful results.
IIowever, in both cases other ratios can be used depending on the
particular starting materials and their pyrolysis
characteristics.
The organosilicon polymers thus formed by reaction of the
organosillcon polymer containing Si-II repeat units witI
preformed ~(RlSiHNII)a(RlSiN)b(RlSi}lNM)C]m,
followed by treatment with an electrophile, henceforth will be
referred to as "graft" polymers.
; Polysilanes of type (RSiH)n (i.e., the general case where
y - 0, x 1) also react with the polymeric silylamides,
[~RlSiHNH)a(RlSiN)b(RlSiHNMC]m. Thus, a reaction
of (C6H5SiH)n with
[(cH3siNH)a(cH3siN)b(cH3sil~NK)c]m ( 1 1 m
ratio) in THF at room temperature gave a new organosilicon
polymer which was found to be an effective ceramic precursor,
giving a Si3N4/SiC/C ceramic product in high yield upon
pyrolysis to 1000C.
Additionally, use of the reaction product of
organopolysilanes or polycarbosilanes with the polymeric alkali
metal silylamide results in a product that is self-curing as the
temperature is raised in the production of ceramic material.
Consequently, with these polymers it is possible to avoid the
formation of SiO2 which results when an oxidative cure step is
used. This again is an improvement over pyrolysis of the
precursor silane compound alone.
~263796
-13-
In this system, R or Ra is preferably a lower alkyl, more
preferably, R or Ra is C113. However, R or Ra need not be
the same and, as aforesaid, mixtures of Si-11 containing
organosilicon compounds and/or repeat units, e.g.,
[(RSiH)x(Rsi)y]n and [(R, SiH)x,(R Si.)y,]n"
[RaSi(H)~(CH2)q] and lRa Si(H)~(CH2)q~]~ and
[(RSiH)X(RSi)y]n and [RaSi(1-1)~(C1i2)q] can be used to
obtain further flexibility in tailoring the properties of the
aforesaid product. Mixed polymers of the type
[(RSi~1)a(RSi)b(RR Si)C~m (where a, b, c, m and R are
as defined above, and R is defined as is R above and R may
be the same or di~ferent th~n R) cnn be used ~s well.
YreEerably, R-R -C113, Ra-Ra ~CH3, Ra-R C113.
Further, these aforesaid mixtures of compounds can be used to
obtain additional flexibility in tailoring the properties of the
aforesaid product.
_
As metnioned, also included in this invention is the case of
[(RSiH)X(RSi)y]n, where x-l, y-O, with R as defined above,
where [(RSiH)]n may be a linear or a mixture of cyclic
species, or a hybrid of both types. For example, [PhSiH]n (Ph
is a phenyl group), cf, Aitken, C. et al., J. Organoll1et. Chem.,
279:Cll-Cl3 (1985), reacts in the same way as the
above-described organopolysilanes to provide new
organopolysilane/organopolysilazane hybrid polymers. These
mixtures will be particularly useful in attempts to avoid excess
free silicon or carbon. The case of aryl-substituted repeat
units of [RaSi(H)~(CH2)q] for example, where Ra is a
phenyl or substituted phenyl group, and Ra can be a lower aryl
group, is also included.
Mixtures of alkali metal polysilazanes, i.e.,
[(RlSiHNH)a(RlSiN)b(RlSiHNE)C]m and
[(Rl Si11N11)a,(Rl SiN)b,(Rl Si11NE)C,]m, (where E
12~3796
-14-
is the moiety introduced by reaction with an electrophile, e.g.,
a lower alkyl group of 1 to 6 carbon atorns, preferably CH3, or
a silyl group), also may be used.
The preceramic product obtained by using alkali metal
silylamides, even in only catalytic amounts, differs from the
starting organosilicon compound. This difference is confirmed
by proton NMR spectra. A typical organopolysilane starting
material when R - CH3 shows an observed proton NMR integration
ratio, SiCH3/SiH, ranging from 3.27 through 3.74 (see Table
1). In contrast, the similar ratio for products obtained when
the starting material is reacted with an alkali metal
silylamide, range from 8.ô to 14.
This difference in products apparently arises because both
Si-H and Si-Si bonds are reactive towards nucleophilic
reagents. Although not wishing to be bound by theory, it is
believed that when alkali metal silylamides are used the
following processes result:
(R3Si)2NM + ,SiH ~siN(siR3)2 + MH (1)
(R3Si)2NM + ,SiH > (R3si)2NH + SiM ~2)
(R3Si)2NM ~-~Si-Si ~(R3si)2N-si~ + SiM~ (3)
In each of the above reactions a new reactive nucleophile is
generated. In the first reaction, this nucleophile is MH, while
in the second and third reactions, the nucleophile is a silyl
alkali metal compound. Thus, nucleophilic attack on the
[CH3SiH)X(CH3Si)y]n system will recur during these
reactions and some of these oligomeric species, which comprise
the starting materials, are linked together, resulting in
products of higher molecular weight. There are other processes
that are possible as well: e.g.,
~2637~
-15-
(R3Si)2NK + -Si ~li (R3Si)2NSi~ K
H ll
~ Si: + Kll
Thus, not only anionic species but also s:ilylenes can be
involved as intermediates.
The "graft" polymer is Eormed by combining the already
formed polymeric alkali metal silylamide with the Si-H
containing organosilicon polymer, for example, the
organopolysilane in varying proportions in an organic solvent.
Thereafter, the mixture is stirred at room temperature for
sufficient time for the two compounds to reac~. Al~y or~nnic
solvent in whlch both polymer systems are soluble without
reaction can be used. Such organic solvents include, for
example, T~F, diethyl ether, glycol ethers, alkanes, arenes and
comblnations thereof. The mixture may be heated above room
temperature, and can be refluxed to speed up the completion of
the reaction. After refluxing, the mixture is quenched with an
electrophile, E-X, to form the organosilicon "graft" polymer.
The electrophile can be an alkyl halide, sulfate, or sulfonate;
a halosilane; or the like. Typically, CH3I or a chlorosilane
is used, although other equivalent electrophiles wel].-known to
those skilled in the art can also be used. E is preferably a
lower alkyl group or silyl group; X preferably a halide, sulfate
or sulfonate.
The organosilicon polymer formed by the present ("graft")
process with the organopolysilane is typically obtained in
yields greater than 85% based on weight of the starting
materials with a variable molecular weight, typical values being
in the 1800-2500 g/mol range. This preceramic organosilicon
polymer can then by pyrolyzed under inert atmosphere conditions
to result in a ceramic material in high yield. Typically,
~Z~379G
-16-
pyrolysis under nitrogen gives ceramic products in a yield of
70-83%.
The organosilicon polymers formed by the present ("graft")
process typically give ceramic yields lO~ to 50~ greater (based
on welght of the starting materials) than the polycarbosilane
(See Table 2) and have a variable molecular weight.
Figure ] is a proton NMR spectrum comparing a l:l by weight
physical mixture of the polycarbosilane and the polysilazane and
a "graft" polymer formed by reacting the polycarbosilane with a
preformed silyamide. The NMR spectrum shows that a new polymer
is obtained when the polycarbosilane and the .silylamide are
heated together in solution and then quenched with methyl
iodide. First, the CH3Si/HSi integrated ratio differ, 9.4 in
the former, 8.7 in the latter. Secondly, ths CH3Si_ NH proton
(at ~ 5.06) to CH3Si_ (at ~ 4.50) proton ratio has
changed from about 2 in the physical mixture to about 1 in the
reaction mixture.
These preceramic organosilicon polymers can then by
pyrolyzed under nitrogen or an inert atmosphere to result in
ceramic materials in high yield. Typically, pyrolysis under
nitrogen gives ceramlc products in a yield o~ G/~-~8~.
What is referred to herein as an "in situ" polymer is
obtained by carrying out the cyclo-(RlSiHNH)n/MH reaction in
solution in the presence of the Si-H containing organosilicon
polymer. In this method, the methylpolysilane or
polycarbosilane is added to an organic solvent. Afterwards, the
cyclo-(RlSiHNH)n mixture (generated by reacting in solution
anhydrous ammonia with RlSiHX2, where Rl is the same as
defined earlier and X is a halogen) is added.
One then adds to the solution a basic catalyst capable of
deprotonating the hydrogen from a nitrogen atom adjacent to a
silicon atom. See U.S. Patent No. 4,482,669. The reaction
~Z63t7~6
-17-
mixture gradually changes color and hydrogen is evolved. The
resulting solutlon is then stirred at room tem~erature Eor
sufficient time for the silylamide intermediates and the Si-11
containing organosilicon polymer to react. It can be heated
above room temperature, and can be heated at reflux to speed the
completion of the reaction. AEterwards, the reaction mixture is
allowed to cool to room temperature, if required, and quenched
with an electrophile such as C113I or a halosilane, such as a
chlorosilane, to produce the organosilicon "in situ" polymer.
The molecular weight of the "in situ" polymer is variable. For
example, typLcal values of the polymer Eormed usin~ an
organopolysilane are between 1600 g/mole to 2750 g/mole. On
pyrolysis this material provides a high yield of a black ceramic
material.
On pyrolysis the polycarbosilane-derived material provides a
yield of a black ceramic material, that is typically lO~ to 50%
greater than that obtained on pyrolysis of the polycarbosilane
(see Table 2).
The organosilicon polymer formed by either of the above
"graft" or "in situ" methods usually is separated from
solution. The solvent is removed by using techniques well known
to a person of ordinary skill in the art. One standard method
is distillation, preferably trap-to-trap distillation. The
polymer, typLcally a white powder that is soluble in an organic
solvent, is thereby obtained. One may also combine trap-to-trap
distillation with centrifuging, followed by trap-to-trap
distillation to separate the polymer from solution.
The "in situ" preceramic polymer differs physically from the
"graft" preceramic polymer. Major differences are observed in
their proton NMR spectra and in the form of their
thermogravimetric analysis (TGA~ curves.
Figure 2 shows the proton NMR spectrum of a graft polymer
lZ~3796
-18-
and that of an "i situ" polymer. Both polymers have similar
starting molar ratios of [(Cll3SiH)x(CH3Si)y]:
(CH3SiHNH), [1.5:1 and 1.45:1, respectively], in terms of
initial reactants used. However, in the " i situ" polymer the
intensity ratio of the ~ 5.1, 4.7 to the ~ 4.0 proton
signals is 12, while in the "graft" polymer this ratio is 1.
The signals around ~ 5.l and 4.7 are due to the Cll3SillN
proton while those around b 4.0 are due to CH3Si_ protons
which are attached to silicon atoms not bound to nitrogen.
Accordingly, this difference in ratio demonstrates that the two
polymers have different structures.
Although not wishing to be bouncl by theory, it appears
likely that in the "i situ" preparation, intermediates formed,
for example, by the action of Kll on (CH3SiHNII)n cyclics also
react with the Si-H containing organosilicon polymer, for
example, the organopolysilane [(CH3SiH)X(CH3Si)y]n
before the polymeric alkali metal silylamide which is the
starting reactant in the "graft" procedure has a chance to be
formed to its usual extent. This results in either less of the
original CH3SiHNH protons being lost and/or more of the Si-H
containing organosilicon system being reacted.
The TGA curve of the "graft" polymer is shown in Figure 3,
while that of the "i situ" polymer is shown in Figure 4. These
two curves differ as well. In the "graft" polymer, the curves
show that there is a small weight loss between 100C and 200 D C
which begins at about 100C. In contrast, with the "in situ"
polymer, the initial small weight loss occurs only at higher
temperatures, approximately beginning at 175C. Both types of
polymers are useful as preceramic materials.
~2~3796
--19--
Table 2
TGA Ceramic Yield of Preceramic Polymer
Wt ratio of Polycarbo- Ceramic Compound
silane: Alkali Metal Yield (Example)
Sil~lamide
100:0 58~ B.(2)
1:1 84~ 37 D.(3)(a)(i)
5:1 67~ III-57 D.(3)(a)(ii)
;
1:1 88~ III-39 D.(3)(b)(i)
5:1 64% III-59 D.(3)(b)(ii)
1:1 86% III-38 E.(2)(a)(i)
5:1 80~ III-56 E.(2)(a)(ii)
1:1 86~ III-40 E. (2)(b)~i)
5:1 66% III-58 E. (2)(b)(ii)
~263796
-20-
The use of the alkali metal silylamide of the formula
[(RlSiHNH)a~RlSiN)b(RlSiHNM)C]m not only improves
the ceramic yield oE the organopolysilanes, but, more
significantly, when this alkali metal silylamide is reacted with
organopolysilane of the formula [(RSill)x(RSi)y]n in the
appropriate stoichiometry, the reaction product of
[(RSiH)X(RSi) ]n and
[(RlSiHNH)a(R~SiN)b(RlSiHNM)C]m (where m and n are
integers greater than l), after treatment with a suitable
electrophile such as an organic or a silyl halide, incorporates
both starting materials. When this reacti.on product is
pyrolyzed, the excess silicon normally obtained in the pyrolysis
of the organopolysilane alone and the excess carbon normally
obtained in the pyrolysis of the quenched polymeric alkali metal
silylamide alone combine so that there is no substantial excess
of either element in the ceramic product. Consequentiy, one can
obtain a ceramic material with less than about 0.1~ of free
silicon and less than about O.l~ of free carbon, i.e., a ceramic
material containing substantially no free carbon and no free
silicon. The exact combination oE the two compounds necessary
to result in the desired stoichiometry can readily be calculated
by a person of ordinary skill in the art on the basis of the
results of the analyses of the ceramic products obtained in the
pyrolysis of the separate polymers. Mole ratios of
organopolysilane : polymeric alkali metal silylamide from about
4:1 to about 1:4, and preferably from 2.5:1 to 1:2 typically
provide useful results. However, other ratios can be used
depending on the particular starting materials and their
pyrolysis characteristics.
The excess of free carbon, which can be a problem with the
starting polycarbosilanes, can be dealt with by using a ternary
system of: (1) the polycarbosilane; (2) the polysilazane (as the
~6~796
-21-
polymeric silylamide, eitller preformed or generated i situ) and
(3) a polysilane whose pyrolysis alone gives a ceramic product
which contains an excess of silicon. Examples of such
polysilanes are organopolysilanes as described above, for
example, those which are produced by the sodium condensation of
methyldichlorosilane. In these reactions the organopolysilane
is preferably as defined above, i.e [(RSiH)X(RSi)y]n.
More preferably R is a lower alkyl group, most preferably R is
CH3. Using an appropriate mixture of the three polymers
(which can be calculated from the results oE the analyse.s of the
ceramic products of the pyrolysis oE each individual polymer,
e.g., the CH3I- quenched polymer in the case of the polymeric
silylamide), one can obtain a ceramic product which contains a
minimal excess of either element, carbon or silicon. Such
hydrid ternary preceramic polymers are soluble in organic
solvents and, depending on component ratios used, are of
variable molecular weight. Their pyrolysis gives black ceramic
products in high (generally > 80%) yield.
Physical blends of Si-H containing organosilicon polymers,
for example the organopolysilane, or the polycnrbosilane
polymers containing repeat units of ~RaSi(H)~(CH2)q]~ for
example, the Yajima polycarbosilane with the "quenched"
[(RlSiHNH)a(RlSiN)b(RlSiHNE)C]m organosilazane
polymer of U.S. Patent No. 4,482,669 can be used since these
react when they are heated together. ~len approximately equal
molar quantities of the polymers where R, or Ra ~ CH3,
- CH3, q - 1 and E ~ CH3, were mixed and finely ground
together and then subjected to pyrolysis to 1000C, ceramic
yields was obtained which were approximately the average of the
ceramic yields when the organopolysilane and the organosilazane
polymers were pyrolyzed separately, and were significantly
~63796
-22-
higher than that which resulted when the polycarbosilane was
pyrolyzed separately ~see Table 2).
When polycarbosilane/orgosilazane mixtures were heated, in
the absence of a solvent at 200C under nitrogen, white foamy
solids were obtalned WhiCIl were insoluble in nollpolar organic
solvents, thus demonstrating ~hat a reaction had occurred below
200C and prior to pyrolysis. When organosilane/
organosilazane mixtures were heated, either in the absence of a
solvent at 100C under nitrogen or in a toluene solution at
rcflux, white powders were obtained which were insoluble in
nonpolar organic solvents, again demonstrating that a reaction
occurred.
Ternary blends of the polycarbosilane, the
[(CH3SiH)X(CH3Si)y]n liquid polysilazane and the
[ (cH3siHN~l)a(cH3siN)b(cH3siHNcH3)c]m
. ~ polysilazane behaved similarly. An obvious reaction occurred
when such a mixture had been heated to 200C, since the
originally soluble mixture became insoluble in organic solvents.
The comblned polymers obtained by the "graft," "i situ" and
physical blend methods can be converted to black ceramic
fibers. Pyrolysis of pressed bars of the combined polymers to
1000C provides a black solid product. In other experiments,
silicon carbide powder was dispersed in a toluene solution
containing 25~ by weight of the combined
organosilane/organosilazane polymers. The solvent was
evaporated and the residue, a fine pow'aer of silicon carbide
k with combined polymer binder was pressed into bars and pyrolyzed
at 1000C. A ceramic bar was obtained showing a low weight loss
and slightly shrunken size.
Similarly, when silicon carbide powder was dispersed in
toluene solutions of the combined polycarbosilane/organosilazane
polymers. The solvent was evaporated and the residue, a fine
1263796
-23-
powder of silicon carbide with combined polymer binder, was
pressed into bars and pyrolyzed at 1000C. A ceramic bar was
obtained showing a low weight loss and slightly shrunken
size.
The invention will be further illustrated by the examples
that follow:
A. General
All glassware was Elame-dried under vacuum or under a stream
of nitrogen prior to use. Tetrahydrofuran t~llF) and benzene
were distilled from sodium and benzophenone ketyl. ~lexane was
distilled from LiAlH4. Solvents were deoxygenated by bubbling
nitrogen through them prior to use. Methyldichlorosilane,
CH3SiHC12, and dimethyldichlorosilane, (CH3)2SiC12,
were commercial products. The polycarbosilane was purchased
from Dow Corning Corporation. Its characterization is reported
below. The ammonolysis of CH3SiHC12 in ether and in THF
solution has been described in U.S. Patent No. 4,482,699 (D.
Seyferth and G.H. Wiseman), as has the reaction of ammonolysis
products, [CH3SiHNH]m, wIth KH to give the polymeric
silylamide, [(CH3SiHNH)a(CH3SiN)b(Cll3SillNK)c)]m
Poly(methydrosiloxane), [CH3Si(H)O]n was purchased from
Petrarch (Catalog #PS 122) and was used as recieved. Piperdine,
diisopropylamine, and propylamine were purchased and were
distilled from CaO before use. Reagent grade sodium shot was
further purified by creating a dispersion in refluxing xylene
and allowing this to cool, with stirring. This served to remove
most of the oxide coating. Anhydrous ammonia was dried further
by passing it through a KOH column.
lH NMR spectra were recorded on a JEOL-FX-9OQ spectrometer
operating at 90 MHz. Elemental analyses were performed by
Galbraith Laboratories, Knoxville, Tennessee. Molecular weights
:'
..
~,%63796
-24-
were determined bymeasuring the free~ing point depression of a
weighed sample of benzene caused by a weighed sample of
product. Thermal analyses were performed using a Perkin-Elmer
TGS-2 Thermogravimetric Analyzer interfacsd with a System 7/4
Thermal Analysis Controller on a DuPont 950 TGA cormected to a
DuPont thermal analysis system. Samples were heated, under
argon, from 25-1000C at a rate of 10C/min. Large scale
pyrolyses were carried out in fused silica boats using a
Lindberg 59344 tube furnace (25-].000C, 10C/min) under
argon atmosphere. scanning electron~icrographs were obtained
using an AM~ lnstrument, operating at 20 KV.
B. Preparation of Organosilicon Compounds
1. Preparation of ~(CH3SiH)X~_3~yln
(all operations under nitro~en) - - i
i
~_~ a. In THF Medium.
A 500 ml, three-necked, round-bottomed flask equipped with a
stir-bar, a dropping funnel and a reflux condenser was charged
with 50.5 g (2-.20 g atom) of Na metal. The flask was attached
to a Schlenk manifold, evacuated and refilled with nitrogen
three times. THF (200 ml) was added and the dropping funnel was
charged with 65 ml (0.625 mol) of CH3SiHC12. The silane was
added to the stirred Na suspension during the course of 45 min.,
after which time the reaction mixture was cloudy and slightly
warm. The mixture was stirred for 16 hours at room temperature
~:. and 48 hours at reflux; it then was cooled to room temperature.
llexane (60 ml) was added. The mixture was transferred by
cannula to a heavy-walled centrifuge bottle and centrifuged.
The supernatant layer was transferred to a 1 liter
round-bottomed flask (under nitrogen). THF (50 ml) and hexane
(30 ml) were added to the resldual solid and the resulting
~LZ63796
-25-
suspension was centrifuged. The supernatant layers were
combined and solvents were removed by t.rap-to-trap distillation
in vacuum until the residual liquid volume was about 100 ml.
This liquid was cannulated into a 250 ml single-necked flask and
the remaining solvent was removed in vacuo to leave 13.2 g (0.30
mol, 48% yield) of a white, glassy solid. On being heated in a
sealed capillary (in vacuo~ this solid soEtened around 40C and
"melted" between 130-140C with gas evolution, leaving a thick
gum There was no further change up to 300C except For a
gradual increase in viscosity. The product was poorly soluble
in hexane, only somewhat soluble in benzene (precluding
measurement of its cryoscopic molecular weight in this solvent)
and quite soluble in THF.
NMR ~90 MHz, in CDC13): ~ 0.10-0.61 (m, SiCH3, 7.5H) and
3.55-3.90 (m, SiH, 1ll). Based on the reasonable assumption that
every Si atom bearing a H substituent also bears a CH3
substituent, the integrated CH3Si and SiH intensities lead to
a constitution [(CH3SiH)o 4(CH3Si)o 6]n
Anal. Calcd for CSiH3 4: C, 27.60; H, 7.87.
Found: C, 27.18; H, 7.17.
IR (KBr, Nujol): 2170(sh), 2100(s, Si-H), 1408(m), 1260(m,
Si-CH3), 1249(s, Si-CH3), 1060(br), lOl9(s), 931(s), 865(vs,
Si-CH3), 770(vs), 685(vs), cm~l.
TGA(25-1000C, 10C/min.): 60% yield of a gray-black ceramic
solid. A tube furnace pyrolysis of 3.20 g of this material to
1500C gave 1.52 g (48%) of a gray ceramic powder.
~_263~96
-26-
Anal. of the Ceramic Powder. Found: C, 22.56; Si, 78.42; H,
0.01; N, 0.009~ (SiC requires C, 29.94; Si, 70.06%; actual
composition: SiC + 0.49 Si). X-ray powder difEraction (d
A): 1.315(s) (~ -SiC), 1.542(s) (~ -SiC), l.91(m)
(Si), 2.181(m), (~ -SiC), 2.52(vs) (a -SiC), 3-13(m)
si) .
A mass spectral analysis of the pyrolysis gas in another
experiment showed the following: no gaseous products were
observed up to 385C, then fragment ions corresponding well with
the reported fragmentation oE Cll35iH3. At 445c,
CH3Sill3 was still observed and a peak at m/z ~ 16 (CH4)
began to grow in. By 5~0C, when weight loss was about over,
only the methane peak was observable. ..
b. In Hexane/T~lF Medium
`~ In a dry box, a 1 liter three-necked, round-bottomed flask
equipped with a stir-bar, a dropping funnel and a reflux
condenser was charged with 75.0 g (3.26 mol) of sodium metal.
The flask was attached to a Schlenk manifold, evacuated and
flushed with nitrogen. THF (70 ml) and hexane (420 ml) were
added and the dropping funnel was charged with 150 ml (1.44 mol)
of methyldichlorosilane. Methyldichlorosilane was added slowly
into the flask over a 3 hour period. The reaction solution
turned purple and by the end of the addition was at gentle
reflux. The reaction mixture was stirred at room temperature
for 2 hours and then heated at reflux for 16 hours. After it
~~ had been cooled to room temperature, the reaction mixture
(except for the large NaCl crystals) was transferred via cannula
into a heavy-walled glass bott].e. The mixture was centrifuged
and the clear, colorless supernatant layer transferred by
cannula into a 1 liter round-bottomed flask equipped with a
~ ~637~6
-27-
stir-bar. Hexane (200 ml) and THF (20 ml) were added to the
remaining solids, the mixture again was centrifuged, and the
supernatant liquid combined with the supernatant solution
previously separated. Solvent was removed by trap-to-trap
distillation until the volume of the residue was about 100 ml,
and the remaining liquid was transferred by cannula into a
weighed 250 ml round-bottomed flask. Remaining solvent was
removed by trap-to-trap distillation at approximately 0.05 mm Hg
at room temperature to give 51.2 g (81%, 1.16 mol) of a cloudy
white oil.
H NMR (90 MHz, C6D6):~ 0.37 (broad, SiCH3, 3.74H)
3.92 (broad, Si}l, l H).
NMR integration of the product gave a constitution of
[(CH3SiH)o 8(CH3Si)0,2]n.
IR (thin film, cm l): 2967(s), 2900(s), 2800(w), 2099(vs),
\~ 1410~s), 1385(w), 1249(s), 1055(br), 933(s), 865(vs), 770(vs),
685(br), 650(sh), 585(w).
Molecular weight (cryoscopic in benzene): 600 g/mol.
Anal, (material from another similar preparation). Calcd. for
CSiH3 76; C, 27.39; H, 8.55; Si, 64.05. Found: C, 27.49; H,
8.98; Si, 61.58%.
TGA (25-1000C, 10C/min): 20% yield of a gray-black ceramic
solid. Pyrolysis of a sample from another preparation in a tube
furnace gave a gray-black ceramic solid in 36% yield (by
weight).
Anal. of Ceramic. Found: C, 22.93; Si, 75.99%.
~-~ The pure liquid obtained by this procedure is very
air-sensitive, particularly when its effective surface area is
high, as when in contact with a fritted funnel or a paper or
cloth towel (in which cases spontaneous inflammation may occur).
Other, si~ilar reactions have given 62-75% yields of
(CH3SiH)X(CH3Si)y. Molecular weight determinations of
~Z63'796
-28-
several preparations ranged from 520-740 g/mol. All products
had very similar lH NMR spectra, but with different
SiCH3:SiH ratios. Physical data of these products are listed
in Table 1.
~v .
~,Z63796
-29-
TABLE 1
PHYSICAL DATA FOR ~(CH3SiH)x(Cll3S~ _ POLYM~RS
Sample # Polymer M.W.a SiCl13:Sillb Cer~micC x y
Yield (%) Yield (~) _
YFY III-l 81 600 3.74:1 20 0.80 0.20
YFY II-40 74 740 3.56:1 16 0.84 0.16
YFY II-25 73 650 3.51:1 26 0.85 0.15
YFY II-12 , 66 520 3.27:1 16 0.91 0.09
YFY I-73 73 680 3.48:1 27 0.86 0.14
aCryoscopic in benzene.
b lH NMR integration ratio.
CUnder nitrogen gas, 25-1000C, 10C/min (TGA)
;,
~Z63796
-30-
For the purposs of simplifying calculation, an average
formula weight value 44 was assigned for the unit
(CII3Si~I)X(CII3Si)y Therefore, in each o~ the following
experiments, the number of moles of the reaction unit (CH3SiH)
was calculated from the weight of the polymer used divided by
44.
The product formed in the TIIF solution,gives a 60~ ceramic
yield, but lt is of limlted solubility in organic solvents and
its conversion to ceramic fibers requires a curing step of
photolysis/oxidation. Preparation of the
[(CH3SiH)X(CH3Si)y]n in a hexane/TllF mixture of
~pI)roxiIlln~oly 6 to 7:1. ros~ o(I 1Il sn~isfnc~ory yi.olds of n
soluble produet. I-Iowever, pyrolysls of this material resulted
in very low eeramie yields, ranging from 16 to 27~. -
' ; ,
.2. Characteri~zation of the Polycarbosilane.
The polyearbosilane, a white solid, was purchased from Dow
Corning Corporation. The following data were eolleeted on it:
H NMR (90 MHz, C6D6): ~ 4.52 (broad, SiH, lH)
0.26 (broad, SiCH3 and
SiC_2Si, 8.6H~
IR (KBr, Nu~ol, em 1): 2104(s), 1253(s), 1014(s, broad),
845(s, broad), 734(s).
Moleeular ~eight (eryoseopie in benzene): 1210 g/mol
TGA (25-1000C, 10C/min): 58~ yield of a blaek eeramie
solid.
Tl/2 - 510C
C. Catalytie Reaetions of ~(CH3SiH~X(CH3Si~yl_
1. Potassium Bis(trimethvlsilvl~amide - Catalyzed
Conversion of ~(CH3SiH~x(CH3Si~yln
~,Z6~796
In a dry box, a 50 ml round-bottomed flask equipped with a
stir-bar, a reflux condenser and a no-air rubber serum cap
("standard apparatus") was charged with 0.1 g of KH (0.0025
mol). THF (20 ml) was added to the flask to suspend the KH. To
the KH suspension was added 0.44 g of [(CH3)3Si]2Nll
(0.0027 mol). Reaction occurred immediately with hydrogen gas
evolution. The solution was stirred at room temperature for 20
mlnutes and then heated at reflux for 20 minutes. The slightly
yellow solution was allowed to cool to room temperature.
Another 100 ml three-necked, round-bottomed flask equipped
with a stir-bar, a reflux condenser and a no-air rubber serum
cap was charged with 2.2 g of [(CH3Slll)x(CH3Sl)y]n
(0.05 mol, x - 0.85, y - 0.15). THF (20 ml) was added to the
flask to dissolve the polymer. The [(CH3)3Si]2NK solution
previously described was slowly added to the reaction flask by
syringe. Addition of each drop resulted in formation of a
transient orange color which quickly disappeared. The orange
color perslsted after 1 ml of the solution had been added.
After 10 ml (ca. 2.5 mol~) of the solution of
[(CH3)3Si]2NK had been added, the reaction mixture turned
deep red and a small amount of white precipitate was present.
CH3I (0.5 ml, 7.9 mmol) was added, and the resulting solution
was stlrred at room temperature for one hour. The solvent was
removed under reduced pressure to give a white solid which was
extracted with two 50 ml portions of hexane. The extracts were
centrifuged, and the clear, colorless supernatant layer was
transferred via cannula into a weighed 100 ml round-bottomed
flask equipped with a stir-bar. Solvent was removed by
trap-to-tràp distillation to give 1.51 g (68~, by weight) of a
white powder ("usual work-ùp"). The reaction product is soluble
in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 4.2 (broad, SiH, 1 H)
0.47 (broad, SiCH3, 8.8 H)
~,2~3796
-32-
Molecular weight (cryoscopic in benzene): 1000 g/mol
TGA (25-1000C, 10C/min~: 63~ yield of a black ceralnic solid,
T1~2 ~ 300Ca
aTl/2 ~ temperature at which one-half oE the total weight
loss has occurred.
2. Potassium Bis(vinvldimethylsilvl)amide - CatalYzed
Conversion of ~(CH3SiH)xtCH3Si~yln
According to the procedure described previously, the
reaction between 0.46 g (0.0025 mol) of
[(CH2-CII)Si(CH3)2]2NH and 0.1 g (0.0025 mol) of KII in 20
ml oE THF was carrled out under nitrogen. The resulting
solution was added to a separate flask which was charged with
2.2 g (0.05 mol) of [(CH3siH)x(cH3si)y]n (x ~ 0.85,
y = 0.15) and 20 ml of THF. After 9 ml (ca. 2.5 mol%) of the
[(CH2-CH)Si(CH3)2]2NK solution had been added, the deep
red reaction mixture started to form small amounts of white
precipitate. CH3I (0.5 ml, 7.9 mmol) was added and the
resulting solution was stirred at room temperature for one
hour. The usual work-up followed. A white powder (2.01 g, 91~)
was obtained which is very soluble in hexane, benzene, and TIIF.
H NMR (90 MHz, C6D6): ~ 4.08 (broad, SiH, llI)
0.47 (broad, SiCH3, 12 H)
Molecular weight (cryscopic in benzene): 850 g/mol
TGA (25-1000C, 10C/min): 61% yield of black ceramic solid,
Tl/2 ~ 400C.
3. Monopotassium Derivative of HexamethylcYclotrisilazane -
Catalvzed Conversion of ~(CH3SiH?x(CH3Si)yln_
According to the procedure described previously, the
reaction between 0.55 g (0.0025 mol) of [(CH3)2SiNH]3 and
0.1 g (0.0025 mol) of KH in 20 ml of THF was carried out under
nitrogen. The resulting solution was added to a separate flask
~2~3796
-33-
which was charged with 2 2 g (0.05 mol) of
[(CH3SiII)X(CH3Si)y]n (x ~ 0.85, y 0.15) and 20 ml of
THF. After 10 ml (ca. 2.5 mol~) of the potassium silylamide
solution had been added, the reaction mixture turned deep red
and a small amount of white solid precipitated. CH3I (0.5 ml,
7.9 mmol) was added, and the resulting solution was stirred at
room temperature for one hour. Work-up as above followed. A
whlte powder (1.95 g, 89~) was obtained. The reaction product
is soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 4.60 (quartet, SiH, 0.7 H)
4.18 (broad, SiH, 1 H)
0.48 (broad, SiCI13, 14 II)
Molecular weight (cryoscopic in benzene): 750 g/mol
TGA (25-1000C, 10C/min): 56~ yield of a black ceramic solid,
Tl/2 300~C.
4. Monopotassium Derivative of sym-TrimethYltrivinYlcYclotri-
silazane- Catalyzed Conversion of
~3 S ~ x ( CH3 S i ~ yln
Essentially the same procedures were used in the reaction of
[(CH3)(CH2-CH)SiNH]3 (0.66 g, 0.0025 mol) with ~I (0.1 g,
0.0025 mol) in 20 ml of THF solution. The resulting solution
was added to a 100 ml three-necked round-bottomed flask which
was charged with 2.2 g (0.05 mol) of
~(CH3SiH)x(CH35i)y]n (x - 0.85, y - 0.15) and 40 ml of
THF. After 6 ml (ca. 1.5 mol~) of the solution had been added,
the deep red color of the reaction mixture persisted and a small
amount of white solid precipitated. CH3I (0.5 ml, 7.9 mmol)
was added, and the resulting solution was stirred at room
temperature for one hour. Work-up as above followed. A white
powder (1.79 g, 81.4%) was obtained. The reaction product is
soluble in hexane, benzene and THF.
1~63796
-34-
H NMR (90 ~l~, C6D6): 5 4.16 (broad, SiH, 1 Il)
0.49 (broad, SiCil3, 8.9 H)
Molecular weight (cryoscopic in benzene): 910 g/mol
TGA (25-lOOO~C, 10C/min): 67~ yield of a black ceramic solid,
Tl/2 = 410C.
5. Potassium Piperidide - Catalvzed Conversion of
~ (CH3SiH)x(CH3~Lyl~
In a dry box, a 50 ml round-bottomed flask equipped with a
stir-bar, a reflux condenser and a no-air rubber serum cap was
charged with 0.1 g of Kll (0.0025 mol). TIIF (20 ml) was added to
the flask to suspend the Kll. To the Kll suspension was added
0.25 ml of piperidine. Reaction occurred immediately with
hydrogen gas evolution. The solution was stirred at room
temperature for one hour and then heated at reflux for one
hour. The slightly yellow solution was allowed to cool to room
temperature.
Another 100 ml three-necked, round-bottomed flask equipped
with a stir-bar, a reflux condenser and a no-air rubber serum
cap was charged with l.l g of [(CH3SiH)X(CH3Si)y]n
(0.025 mol, x - 0.8, y - 0.2). THF (20 ml) was added to the
flask to dissolve the polymer. The potassium piperidide
solution previously described was added slowly to the reaction
flask by syringe. Addition of each drop resulted in formation of
a transient orange color which quickly disappeared. The orange
color persisted aEter 10 ml of the solution had been added.
AEter 20 ml (ca. 10 mol~) of the solution of cyclo-C5HlONK
had been added, the reaction mixture was stirred at room
temperature for one hour. The reaction solution turned deep red
and a small amount of white precipitate was present. CH3I
(0.5 ml, 7.9 mmol) was added, and the resulting solution was
stirred at room temperature for one hour. The solvent was
removed by trap-to-trap distillation at reduced pressure to give
~263796
a white solid which was extracted with two 35 ml portions of
hexane. The extracts were centrifuged, and the clear, colorless
supernatant layer was transferred via cannul.a into a weighed 100
ml round-bottomed flask equipped with a stir-bar. Solvent was
removed by trap-to-trap distillation to give 1.03 g (67~, by
weight) of white powder which is soluble in hexane, benzene, and
TIIF.
H NMR (90 MHz, C6D6): 6 4 09 (broad, Sill, 1 }l)
0.47 (~road, SiCl13, ~.7 Il)
Molecular weight (cryoscopic in benzene): 840 g/mol
TGA (25-1000C, 10C/min): 57~ yield of a brownish-black ceramic
solid
Tl/2 ~ 350OC.
6. Potassium n-Propylamide - Catalyzed Conversion of
~(CH3SiH)x(c~13si)~ln
Essentially the same procedure was used in the reaction of
0.30 g (0.0025 mol) of n-C3H7NH2 with 0.1 g (0.0025 mol)
of Kll in 20 ml of THF as that described in Section C.(5). In
this case, 20 ml of the n-C3H7NIIK solution (ca. lO mol~) was
used to react with l.l g (0.025 mol) of
[(CH3SiH)X(CH3Si)y]n (x ~ 0.8, y 0.2) in 20 ml of
THF. After the addition was completed, the reaction solution
turned orange and was stirred at room temperature for one hour.
The solution turned deep red and a small amount of white
precipitate was present. CH3I (0.5 ml, 7.9 mmol) was added,
and the resulting solution was stirred at room temperature for
one hour. The usual work-up left 0.95 g (73% by weight) of a
white solid which is soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6) 6 4.08 ~broad, SiH, l H)
0.51 (broad, SiCH3, 13.6 H)
Molecular weight (cryoscopic in benzene) : 840 g/mol
~L2637~i
-36-
TGA (25-1000C, 10C/min): 57% yield of a brownish-black
ceramic solid
Tl/2 ~ 300C
7. Potassium Diisovropylamide - Catalyzed Conversion of
l(cH3siH)-(cll3si)yl-
Essential].y the same procedure was used in the reaction of
0.30 g (0.0025 mol) oE (iso-C3H7)2NII wlth 0.1 g (0.0025
ol) oE ~l in 20 ml o~ Tlll as ~llat described in Section C.(5).
In this case, 20 ml of the (iso-C31l7)2NK solution (ca. 10
mol~) was used to react with 1.1 g (0.025 mol) of
[(CH3SlH)X(CH3Si)y]n (x ~ 0.8, y ~ 0.2) in the 20 ml
of THF. After the addition was completed, the reaction solution
turned orange and was stirred at room temperature for one hour.
The solution turned deep red and a small amount of white
preclpltate was present. CH3I (0.5 ml, 7.9 mmol) was added,
and the resultlng solution was stirred at room temperature for
one hour. Work-up as above left 1.03 g (79% by weight) of a
white solid which i5 soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 3.99 (broad, SiH, 1 H)
0.47 (broad, SiCH3, 8.7 H)
Molecular weight (cryoscopic in benzene): 750 g/mol
TGA (25-lOOO~C, lOrC/min): 34% yield of a brownish-black solid
Tl/2 = 280C
D. "Graft Procedure"
1. Reactions of
~(CH3SiHNH)a(CH3SiN)b(CH3SiHNK)clm Livin~ Polymer
3 ~ x~CH3Sl)yln
a ~(CH3SiH~x1__3Si)yln Prepared in 7:1 Hexane/THF
i. Using cyclo-~CH3SiHNH]m Pre~ared in Diethyl
Ether
1~6~796
-37-
The same general procedures were used for all of these
reactions. In a dry box, a 250 ml round-bottomed Elask equipped
with a stir-bar, reflux condenser and a serum cap was charged
with a weighed smount of Ktl (ca. 3. 3 mol~) based on
(CH35itlNtl) ) . THF (100 ml) was added to suspend the KH.
(CH3SiHNH)m, prepared in ether solution, was added into the
flask by syringe (a vigorous reaction occurred and a large
amount of H2 gas was evolved which was vented o.tt oE the flask
tllrougll nn oil bu~bler. A~ter ~lle addition wns Llnislled, the
reaction mixture was stirred at room temperature for 1 hour and
then heated at reflux for l hour.
A separate 250 ml flask equipped with a septum, reflux
condenser and stir-bar was charged with a weighed amount oE
[(CH3siH)X(cH3si)y]n (x - 0.85, y - 0.15). TilF (60
ml) was added by syringe to give a clear, colorless solution.
The living polymer solution previously described was cannulated
slowly into the reaction flask. The resulting orange solution
was stirred at room temperature for one hour and then heated at
reflux for one hour. The reaction mixture was allowed to cool
to room temperature and 0.5 ml (7.9 mmol) of CH3I was added
and the volatiles were removed by trap-to-trap distillation.
The product was treated with 200 ml of hexane and the insoluble
residue removed by centrifugation. The hexane was removed from
the supernatant solution by trap-to-trap distillation, leaving a
white solid. Physical data for these reaction products are
given in the Tables 3, 4, 5, and 6. All of these polymers are
very soluble in hexane, benzene, and THF.
b. Using cyclo- ~C113SitlNtll~ Prepared in TIIF
According to the procedure described previously, the
reactions between KH and (CH3SiHNH)m (prepared in THF
12~3796
-38-
solution) were carried out under nitrogen. The living polymer
solution then was added to the THF solution of
[(C113Si~)x(CH3Si)y]n (x = 0.8, y = 0.2). The
resulting orange solution was stirred at room temperature for
one hour and then heated at reElux for one hour. The reaction
mixture was allowed to cool to room temperature and 0.5 ml (7.9
mmol) of CH3I was added. Work-up as described in the previous
experiment left a white solid. Physical data for these reaction
produc~s are ~iven in ~lle Tn~lcs 3, 4, 5, nnd G.
.~
_
12637~6
-39-
TABLE 3
PREPARATION OF TIIE MIXED POLYMERS
Sample ~ YFY YFY YFY YFY YFY YFY
III-7 III-ll III-14 II-29 II-30 II-30-1
Solvent for
(CH3sillNH)m
PreparationTHF THF THF Ether Ether Ether
Weight of
[(CH3siH)x10.1 g6.6 g 3.3 g 2.4 g 1.1 g 2.2 g
(CH3sl)y~n
i'-
~:.
Moles of
[(CH3siH)x0.23 0.15 0.075 0.055 0.025 0.05
(CH3Si)y)n
(A)
Weight of
(CH3slllNH)m 8.85 g8.85 g 8.85 g 2.4 g 2.08 g 1.22 g
Moles of
(C1~3SiHNH)m
;~ ~ (B)0.15 0.15 0.15 0.041 0.035 0.021
Mole Ratio
A:B 1.5:1 1:1 1:2 1.34:1 1:1.41 2.42:1
Yield (%) 85 88 87 90 95 88
lZ63796
--~o--
TABLE 4
CERAMIC YIELD AND MOLECULAR WEIGHT DATA OF MIXED POLYMERS
Sample #d Ceramica 1/2 MolcularC
Yield (~) _ (C) Wei~llt(g/mol)
YFY III-7 74 420 1800
YFY III-ll 78 420 2600
YFY III-14 83 560 2500
YFY II-29 78 460 2000
YFY II-30 78 470 2000
YFY II-30-1 76 400 2000
aUnder nitrogen, 25-1000C, 10C/min (TGA)
bTemperature at which l/2 of total weight loss had cccurred
. . ~
CCryoscopic in benzene
dFor detalls of preparation, see Table 4
lZ63796
-41-
TABLE 5
l_ NMR SPECTRAL DATA- OF THE MIXED POLYMERS
Sample #c (CH3SiHNH) (Cll3SiH) (Cll3SiHNH) Integration
and SiC113_ Ratio=
YFY III-7 5.12 (b) 4.12 (b) 1.56, 1.22, 1:1:14.4
4.G7 (b) 0.88,
0.46 (b),
0.24
Y~Y III-ll 5.14 (b) 4 07 (b) 1.56, 1.22, 1.75:1:7
4.67 (b) 0.88,
0.41 (b),
0.24
YFY III-14 5.19 (b) 4.08 (b) 1.55, 1.23, 3:1:18
4.71 (b) 0.89,
0 45 (b),
0.26
YIY II-29 5.17 (b) 4 o5 (b) 1.35, 2:1:14.6
4.72 (b) 3.56 (b) 0.52 (b),
0.27
YFY II-30 5.17 (b) 4 03 (b) 1.41, 1.34, 2.13:1 13.8
4.71 (b) 3.56 (b) 1.22,
0.46 (b),
0.27
YFY II-30-1 5.15 (b) 4.12 (b) 1.23, 1.9:1:16.1
4.72 (b) 3.57 (b) 0.46 (b)
0.26
. _ . ... _ _
a90 MHz, in C6D6, chemical shift in ppm.
b(CH3SiHNH)/(CH3Si_)/(C_3Si)+(N_) proton integration
CFor details of preparation, see Table 4
12~37!~6
-42-
TABLE 6
PROPOSED FORMULAS AND TIIEIR ANALYTICAL DATA FOR TIIE MIXED POLYMERS
Proposed Formula
(CH3SiH)x(CH35i)y(CH3SiHNII)a(C~13SiN)b
Sample f~f Polymera Totalg Ceramic Total
Anal. Accounted Anal. Accounted
Calcd. Found ForFound For
YFY III-7 x, 0.163 C, 24.46 C, 25.75 96.8 C, 20.59 97,27b
y, 0.437 ~1, 7.11 Il, 7.69 Il, 0.78
a, 0.163 Si, 57.02 Si,53.42 Si, 62.79
`- b, 0.238 N, 11.41 N, 9.94 N, 13.11
YFY III-ll x, 0.116 C, 23.78 C, 24.79 98.49 C, 19.28 101.0C
y, 0.384 H, 6.97 H, 7.34 H, 0.99
a, 0.203 Si, 55.41 Si,53.17 Si, 63.47
b, 0.297 N, 13.85 N, 13.19 N, 17.26
YFY III-14 x, 0.09 C, 22.65 C, 24.21 100.46 C, 18.27 90.44
y, 0.24 H, 6.85 H, 7.85 H, 0.55
a, 0.27 Si, 52.81 Si, 51.89 Si, 58.65
b, 0.40 N, 17.69 N, 16.51 N, 12.97
YFY III-29 x, 0.087 C, 24.26 C, 24.03 87.06 C, 19.68 95.0ld
y, 0.482 H, 6.94 H, 7.97 H, 0.19
`- a, 0.174 Si, 56.56 Si, 43.56 Si, 58.71
b, 0.256 N, 12.17 N, 11.50 N 16.43
YFY III-30 x, 0.112 C, 22.73 C, 24.56 90.53 C, 17.31 95.39e
y, 0.303 H, 8.76 H, 6.97 H, 0.20
a, 0.239 Si, 53.00 Si, 44.56 Si, 57.87
b, 0.346 N, 15.50 N, 14.44 N, 20.01
~2~3796
-43~
YFY II-30-1 x, O.062C, 25.33 C, 23.35 79.45 C, 19.97 90.36
y, 0.646H, 6.98 Il, 6.88il, 0.65
a, 0.122Si, 59.06 Si, 41.53Si, 58.44
b, 0.172N, 8.62 N, 7.69N, 11.30
-
aCalculated on the basis of NMR integratlon
bCalcd- compo5ition (Si3N4~ Si3N4 -~ 6.6 SiC -~ 0.74 C
this repre3ents only 2.2 % by weight free carbon
CCalcd. composltion: Si3N4 + 4.4 SiC + 0.85 C
(equivalent to 3.1~ by weight Eree carbon)
dCalcd. composition (assuming % Si is in error):
Si3N4 + 4.8 SiC + 0.84 C
(equivalent to 2.9~ by weight free carbon)
eCalcd. composition (same assumption): Si3N4 + 3.3 SiC + 0.78C
~equivalent to 3.3% by weight free carbon)
For details of preparation, see Table 4
gAnalytical difficulties, probably due to formation of ceramic
material
~Z6;~796
-44-
b. ~(CiI3Sil-I)X(CII3Si) ln PrePared in THF
i. U~in~ cvclo~ H35iHNII)Im PreDared in Diethyl Ether
In a dry box, a 250 ml round-bottomed flask equipped with a
stir-bar, reflux condenser and a serum cap was charged with 0.01
g (0.25 mmol) of KII. TIIF (100 ml) was added to suspend the ~I.
To the KH suspension, (CII3SiHNIl)m (1.57 g, 0.027 mol,
prepared in ether solution), was added by syringe (a vigorous
reaction occurred and a large amount of H2 gas was evo].ved
whlch was vented out of the flask through an oil bubbler).
After the addition was finished, the reaction mixture was
stirred at room temperature for 1 hour and then at reflux for 1
hour.
A separate flask equipped with a septum, reflux condenser
and stir-bar wa5 charged with 1.1 g (0.025 mol) of
[(CII3SiH)X(CH3Si)y]n (x ~ 0.46, y ~ 0.54). TIIF (60
ml) was added by syringe to give a clear, colorless solution.
The living polymer solution described above was carmulated
slowly into the reaction flask. The resulting orange solution
was stirred at room temperature for one hour and then heated at
reflux for one hour. The reaction mixture was allowed to cool
to room temperature and 0.5 ml (7.9 mmol) of CH3I was added
and the solvent was removed by trap-to-trap distillation,
leaving a white solid (2.5 g, 94% by weight). The reaction
product is soluble in hexane, benzene, and TIIF.
11 NMR (90 MHz, C6D6) ~ 5.20, 4.74 (broad, SiCH3HNH,
1.25H)
4.07 (broad, SiCH3_, lH)
1.59,1.23 (broad, SiCH3HNH, lH)
0.46, 0.26 (broad, SiCH3, 11 H)
Molecular weight (cryoscopic in benzene): 1700 g/mol
TGA (25-1000C, 10C/min): 76~ yield of a black ceramic solid,
Tl/2 - 400C.
~263~796
-45-
ii. Uslng cyclo-~C113SillNIllm Prepared in THF
According to the procedure described previously, the
reactions between KH (0.1 g, 2.5 mmol) and (C113SillNII)m (2.9
~, 0.051 mol, prepared ln Tlll solu~lon) were carried out uncler
nitrogen. The living polymer solution then was added to the THF
solution of [(CH3SiH)X(CH3Si)y]n (2-2 g, 0-05 mol~ x =
0.46, y - 0.54). The resulting orange solution was stirred at
room temperature for one hour and then heated at reflux for one
hour. The reaction mixture was allowed to cool to room
temperature and 0.5 ml (7.9 mmol) of C113I was added. Work-up
as described in the previous experiment left a white solid (4.65
g, 91% by weight). The reaction product is soluble in hexane,
benzene, and THF.
11 NMR (90 Mllz, C6D6): ~ 5.15, 4.71 (broad,SiCH3llNII,
2 H)
4.50, 3.93 (broad, SiCH3_, 1 H)
1.58, 1.23 (broad, SiCH3HNH, 1 H)
0.47, 0.25 (broad, SiC_3,16 H)
Molecular weight (cryoscopic in benzene): 2700 g/mol
TGA (25-1000C, 10C/min): 80~ yield of a black ceramic solid,
Tl/2 420C.
2. Reaction of Polymeric ~(C6_5SiH~ln with
Poly(phenylsllylene), [C6H5SiH]n, molecular weight
860, was prepared by the method of Aitken, et al., J. Organomet.
Chem., supra.
The polymeric silylamide was prepared by the usual method,
in this case by adding 1.0 g (3.0 mmol) of cyclo-(CH3SiHNH)m
(mol. wt 330), obtained by ammonolysis of CH3SiHC12 in
diethyl ether, to a suspension of 0.02 g (0.5 mmol) of KH in 10
ml of THF at room temperature. The mixture was stirred at room
12637916
-46-
temperature for two hours. This solution then was added, under
dry nitrogen, to 1.0 g of (C6H5SiH)X (1.2 mmol) in 20 ml
of THF in a 100 ml three-necked flask equipped with reflux
condenser topped with a nitrogen inlet tube, two rubber septa
and a magnetic stir-bar, at room temperature. The reaction
mixture turned orange upon addition of a few drops of the
polysilylamide solution. (The final color was re~.) After the
reaction mixture llad been stirrecl at room tcmperature fcr three
days, 0.1 g of methyl iodide was added. One-half of the THF was
removed in vacuo and 20 ml of hexane was added. Centrifugati.on
gave a clear supernatant solution which was evaporated in vacuo
to leave an ofE-white powder, 1.90 g (95~ yield).
Analvsis: Found: C, 45.54; Il, 6.08; N, 12.31; Si, 36.37%.
lH NMR (C6D6): ~ 0.2-1.4 (broad, SiCH3, 0.58H)
... 4.6-5.8 (broad, SiH, 0.16 H)
6.5-7.7 (broad, SiC6H5, lH).
Molecular weight (cryoscopic in benzene): 1470 g/mol
TGA (25-1000C, 10/min): 78% yleld of a black ceramic solid.
Pyrolysis of a larger sample in a tube furnace to 1000C gave a
black ceramic solid in 74% yield.
Analysis: Found: C, 39.93; H, 0.54; N, 15.41; Si, 44.29~.
From these data a composition 1 Si3N4 + 2.75 SiC + 9.4 C may
be calculated.
A similar preparation in which the
polysilylamide/poly(phenylsilylene) mole ratio used was 5 gave a
soluble white powder, molecular weight 2360, as a product whose
` pyrolysis to 1000C gave an 86% ceramic yield.
3. Reactions of
~(cH3siHNH)a(cH3siN~b~cH3siHNK)clm
Living Polymer with PolycarbosiTa-ne .
a, Using Cyclo-(CH35iHNH)m Prepared in Diethvl_Ether.
i. Polycarbosilane/[CH35iHNH]m in l:l weight ratio
(III-37).
~263796
-47-
In a dry box, a 250 ml round-bottomed flask equiped with a
stir-bar, reflux condenser and a serum cap was charged with 0.15
g ~3.75 mmol) of K~l (4.4 molG, based on (C113SillNII)). THF (50
ml) was added to suspend the KH. (CH3SillNHjm (5 g, 0.085
mol, in 80 ml of TIIF), prepared by C113SiUC12 ammonolysis in
ether solution, was added into the flask by syringe. A vigorous
reaction occurred and a large amount of H2 gas was evolved
whlch was vented out oE the flask through an oi:L bubbler. After
the additlon was finished, the reaction mixture was stirred at
room temperature for 2 hours.
A separate 250 ml round-bottomed flask equipped with a
septum, reflux condenser and stir-bar was charged with 5.0 g of
polycarbosilane. TIIF (50 ml) was added by syringe to give a
clear solution. The living polymer solution previously
described was cannulated slow].y into the reaction flask. The
`~ resulting clear solution was stirred at room temperature for two
hours and then heated at reflux for 24 hours. The reaction
mixture was allowed to cool to room temperature and 0.5 ml (7.9
mmol) of CH3I was added, the mixture was refluxed for 2 hours
and the solvent was removed by trap-to-trap distillation. The
product was extracted with 200 ml of hexane and the insoluble
residue removed by c~ntrifugation. The hexane was removed from
the supernatant solution by trap-to-trap distillation, leavlng
9.6 g (969~ yield by weight) of a white solid. The polymer is
very soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 5.02, 4.55 (broad, SiH, lH)
~- 1.56, 1.23, 0.88 (SiCH3NH)
0.25, O.la (broad, SiCH3, SiC1129.4U,
for the total area of SiC_3
SiCH2 and SiCH3NH)-
Molecular weight (cryoscopic in benzene): 1550 g/mol
~ Z63796
-4~-
TGA (25-1000C, 10C/min): 8~1% yield of a black ceramic
solid.
Tl/2 - 640C. (Tl/2 = temperature at which one-halE of
weight loss has occurred.)
Melting point (sealed capillary under vacuum): Does not melt at
temperatures up to 320C.
Analysis: Found: C, 32.00; H, 7.47; Si, 48.25; N, 11.87
Tot~l: 99.59%
Ceramic ~nalysis: Large scale pyrolysis of the sample under
N2 to give 77~ yield of a black ceramic solid (25-1000C,
10/C/min).
Found: C, 25.54; Il, 0.62; Si, 53.04; N, 15.55
Total: 94.75~
Composition:l SiC + 0.2 Si3N4 + 0.7C
(equivalent to 10.5 weight % of free carbon)
! ii. Polycarbosilane/lCll3SillNHln in 5:1 Weight
Ratio (III-57).
According to the procedure descrlbed previously, the
reaction between 0.05 g (1.25 mmol) KH and 1.0 g (0.017 mol)
(CH3SiHNH)m (prepared in ether solution) in 100 ml of THF
was carried out under nitrogen. The living polymer solution
then was added to the THF (50 ml) solution of the
polycarbosilane (5.0 g). The resulting solution was stirred at
room temperature for 16 hours. To the reaction mixture 0.5 ml
(7.9 mmol) of CH31 was added and the mixture was refluxed for
2 hours. Work-up as described in the previous experiment left
5.8 g (97% yield by weight) of a white solid. The polymer is
very soluble in hexane, benzene, ~nd TIIF.
H NMR (90 MHz, C6D6: ~ 5.00, 4.55 (broad, Si_, 1l-l)
1.22, 0.88 (SiCH3N_)
0.30 (broad, SiCH3 and SiCH2 9H,
for the total area of SiCH3,
SICH2 and SiCH3NH)
1263796
--~19--
Molecular weight (cryoscopic in benzene): 1100 g/mol
TGA (25-1000C, 10C/min): 67~ yield of a black ceramic
solid.
Tl/2 ~ 520C.
Melting point (sealed capillary under vacuum): Softens at
220C, melts at 240C (to a thick gum), no further change up
to 300C.
b. Usin~ CYC10 (CH3SiHNH?m Pre~ared in T~IF.
i. Polycarbosilane/~Cll3SiHNIIm in 1:1 weight
ratio (III-39~ - -
In a dry box, a 250 ml round-bottomed flask equipped with a
stLr-bar, reflux condenser and a serum cap was charged with 0.15
g (3.75 mmol) of KH (4.4 mol~, based on (CH3SiHNH)). THF (50
ml) was added to suspend the KH (CH3SiHNII)m (5.0 g, 0.085
mol, in 80 ml of THF), prepared by ammonolysis of CH3SiHC12
i in THF solution, was added into the flask by syringe. A
vigorous reactlon occurred and a large amount of H2 gas was
evolved which was vented out of the flask through an oil
bubbler. After the addition was finished, the reaction mixture
was stirred at room temperature for 2 hours.
A separate 250 ml round-bottomed flask equipped with a
septum, reflux condenser and stir-bar was charged with 5.0 g of
polycarbosilane. THF (50 ml) was added by syringe to give a
clear solution. The living polymer solution previously
described was cannulated slowly into the reaction flask. The
resulting solution was stirred at room temperature for two hours
and then heated at reflux for 24 hours. The reaction mixture
was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of
CH3I was added, the mixture was heated a few hours, and the
solvent was removed by trap-to-trap distillation. The product
was extracted with 200 ml of hexane and the insoluble residue
removed by centrifugation. The hexane was removed from the
lZ6379~i
-50-
supernatant solution by trap-to-trap distillation, leaving 9.7 g
(97% yield by weight) of a white solid. The polymer is very
soluble in hexane, benzene and THF.
H NMR (90 MHz, C6D6) ~ 5.33, 4.58 (broad, Sl}l, lH)
1.37, 1.25, 0.91 (SiCH3NH)
0.29, 0.22 (broad, SiCH3,
SiCH2, 9.9H, for the total
area of SiCH3 SiC_2 and
SlCl13NH)-
Molecular weight (cryscopic ln benzene): 2360 g/mol
TGA (25-1000C, 10C/min): 88% yield of a black ceramic
solid Tl/2 - 670C.
Melting point (sealed capillary under vacuum): Does not melt at
temperatures up to 320C.
Analysls: Found: C, 31.88; ~l, 7.52; Sl, 49.16; N, 11.69
Total: 100.25%
Ceramic Ana~ : Large scale pyrolysis oE the sample under
argon gave an 80% yleld of a black ceramic solid (25-1000C,
10C/min).
Found: C, 24.03; Il, 0.77; Sl, 60.72; N, 14.72
Total: 100.24%
Composition: lSiC + 0.2 Si3N4 + 0.45 C
(equivalent to 7.5 weight ~ of free carbon)
ii. Polvcarbosilane/LC~3SiHNHlm in 5:1 Weight
Ratio (III-59).
, According to the procedure described previously, the
reactions between 0.005 g (1.25 mmol) KH and 1.0 g (0.017 mol)
(CH3SiHNH)m (prepared in THF solution) in 100 ml of THF were
carried out under nitrogen. The living polymer solution then
was added to the THF (50 ml) solution of polycarbosilane (5.0
g). The resulting solution was stirred at room temperature
126379~
-51-
overnight. To the reaction mixture 0.5 ml (7.9 mmol) of CH3I
was added and the mixture was refluxed for 2 hours. Work-up as
described in the previous experiment left 5.9 g (98% yield by
weight) of a white solid. The polymer is very soluble in
hexane, benzene, and TIIF.
lH NMR (90 MHz, C6D6): ~ 5.07, 4.55 (broad, SiH, l11)
1.24, 0.89 (SiCH3NII)
0.28 (broad, SiCH3, SiCl-12
7.5}1, Eor the total area of
SiCH3 SiCH2 and SiC113NH).
Molecular weight (cryoscopic in benzene): 970 g/mol.
TGA (25-1000C, 10C/min): 64% yield of a black ceramic
solid Tl/2 - 530C.
Melting point (sealed capillary under vacuum): Softens at
240C, melts at 265C, no further change up to 300C.
E. "In-Situ Procedure"
1. Reaction of a Mixture of CX~lic [CH3SiHNIIlm and
iH-~(c~-l3si)yl ~ th K~ Cat.~].Yst ~
a. Using cYclo- ~C113SillN11)]m Prepared in Diethyl Ether
In a dry box, a 250 ml round-bottomed flask equipped with a
stir-bar, reflux condenser and a serum cap was charged with 0.10
g of KH (0.0025 mol). THF (50 ml) was added to suspend the KH.
A separate 250 ml Schlenk flask was charged with 2.0 g of cyclic
(CH3SiNHN)m (0.034 mol), prepared by ammonolysis of
CH3SiHC12 in ether solution, and 2.2 g of
[(CH3SiH)X(CH3Si)y]n (0.05 mol, x ~ 0.74, y = 0.26),
and lO0 ml of THF. The mixed polymer solution was transferred
by cannula into the KH suspension. The reaction mixture
gradually changed color to light orange and hydrogen gas was
slowly evolved. The resulting solution was stirred at room
temperature for 14 hours and then heated at reflux for l hour.
~2~;3~79~
-52-
The light orange color of the solution persisted. The reaction
mixture was allowed to cool to room temperature and 0.5 ml (7.9
mmol) of CH3I was added. The solvent was removed by
trap-to-trap distillation. The product was extracted with 200
ml of hexane and the insoluble residue removed by
centrifugation.
The clear, colorless supernatant layer was transferred via
cannula into a weighed 250 ml round-bottomed flask The hexane
was removed by trap-to-trnp dis~illation Lenvin~ 3.8 ~ (91% ~y
weight) of A white powder. The latter is soluble in TllF,
benzene, and hexane.
H NMR (90 Mtlz, C6D6):~ 5.19, 4.70, 3.97 (broad, SiH,
1 H)
1.30, 0.47, 0.26 (broad, SiCH3 and NH
3.6 H)
Molecular weight (cryoscopic): 1650 g/mol
TGA (25-1000C, 10C/min): 62% yield of a black ceramic solid,
Tl/2 - 380C
Anal, of Polymer Product: Found: C, 23.56; tl, 7.37; N, 14.51
Si, 50.89%
A sample of the ceramic product obtained in a tube furnace
pyrolysis was analyzed:
Found: C, 19.30; N, 19.58;
SL, 57.94; 0, 2.05%
From this analysis one may calculate a ceramic composition:
1 SiC + 0.37 Si3N4 + 0.68 C + 0.07 SiO2
(equivalent to 7.9~ by weight free carbon)
b. ~sing cyclo-[Cll3SillNtl]m Prepared in TtlF
According to the procedure described above, the reaction
between 0.1 g of K~l (0.0025 mol), 2.0 g of cyclic
~IZ6;~79~
-53-
(CH3SiHNH)m (prepared in THF solution), and 2.2 g of
[(C113SiH)x(CH3Si)y]n (x = 0.74, y ~ 0.26) was carried
out under nitrogen. The resulting reaction mixture also
gradually changed color to light orange with slow evolution of
hydrogen gas. The solution was stirred at room temperature for
14 hours and then 0.5 ml (7.9 mmol) of C113I was added. Work-up
as described in the previous experiment left a white, soluble
solid (3.75 g, B9%).
H NMR (90 ~-lz, C6D6):~ 5.13, 4.72, 3.98 (broad,SiH,
1 Il)
1.29, 0.48, 0.26 (broad, SiCH3 and Nll,
3 7 H)
Molecular weight : 2750 g/mol
TCA (25-1000C, 10C/min): 73~ yield of a black ceramic solid,
Tl/2 360 C.
Anal. of Polymer Product: Found: C, 24.16; H, 7.14; N, 15.26;
Si, 51.20~
A sample of the ceramic product obtained in a tube furnace
pyrolysis was analy7ed:
Found: C, 19.81; N, 19.77;
Si, 58.14; 0, 1.67
From this analysis one may calculate a ceramic composition:
1 SiC + 0.37 Si3N4 + 0.7 C + 0.05 SiO2
(equivalent to 8.1~ by weight free carbon)
~- 2. Reactions of a Mixture of Cyclic [CH3SiHNH13 and
Polvcarbosilane with KH Catalvst.
~263796
-54-
a. Usin~ CYC10 ICH3SiHNHIm Prepared Erom Diethyl Ether.
i. Polycarbosilane/~CII3SiIINHlm in 1:1 weight
ratio (III-38).
In a dry box, a 250 ml round-bottomed flask equipped with a
stir-bar, reflux condenser and a serum cap was charged with 0.15
g of ~I (3.75 mmol). THF (50 ml) was added to suspend the KH.
A separate 250 ml Schlenk flask was charged wtih 5.0 g of
(CH3SiHNH)m (0.085 mol), prepared in ether solution, and 5.0
g of polycarbosilane, and 150 ml of TIIF. The mixed polymer
solution was transferred by cannula into the ~I suspension in
THF. The reaction mixture gradually turned clear and hydrogen
gas slowly evolved. The resulting solution was stirred at room
temperature for 2 hours and then heated at reflux for 24
hours. The reaction mixture was allowed to cool to room
temperature and 0.5 ml (7.9 mmol) of CH3I was added and the
mixture was heated for several hours. The solvent was removed
by trap-to-trap distillation. The product was extracted with
200 ml of hexane and the insoluble residue removed by
centrifugation. The clear, colorless supernatant layer was
transferred via a cannula into a weighed 250 ml round-bottomed
flask. The hexane was removed by trap-to-trap distillation
leaving 9.7 g (97% yi.eld by weight) of a white powder. The
white powder is soluble in THF, benzene, and hexane.
H NMR (9OMHZ,C6D6) ~ 5.10, 4.55 (broad 5:H, lH)
1.56, 1.22, 0.88 (SiCH3NH)
- 0.26, 0.19, (broad SiCH3, and
`~ SiCH2 9.1H, for total area of
SiCH2 and SiCH3N~I)
Molecular weight (cryoscopic in ben~ene): 2150 g/mol
TGA (25-1000C, 10C/min): 86~ yield of a black ceramic
solid Tl/2 ~ 670C.
~263796
_~)rj_
Melting point (sealed capillary under vacuum): Does not melt at
temperatures up to 320C.
AnalysLs: Found: C, 31.87; 11, 7.55; Si, 48.93; N, 11.70
Total: 100.05%
Ceramic Analvsis: Large scale pyrolysis of the sample under
N2 to give 74% yield of a black ceramic solid (25-1000C,
10C/min).
Found: C, 24.79; H, 0.70; Si; 56.79; N, 15.80
Total: 97.38%
Composition:l SlC ~ 0.2 Si3N4 ~ 0.6 C
(equivalent to 9.6 weight % of free carbon)
ii. Polycarbosilane/~C1l351l-lNI{~n~ in 5;1 wei~ht
ratio (III-56).
According to the procedure described previously, the
reactions between 0.05 g of Kll (1.25 mmo].), 1.0 g oE
[CH3SiHNH]m (prepared in ether solution), and 5.0 g of
polycarbosilane was carried out under nitrogen. The resulting
1 reaction mixture also gradually turned clear with slow evolution
of hydrogen gas. The solution was stirred at room temperature
for 3 hours and then heated ar reflux for 2 hours. The solution
was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of
C}13I was added and the mixture refluxed for several hours.
Work-up as described in the previous experiment left a white
solid (5.8 g, 97% yield by weight). The white powder is soluble
in THF, benzene and hexane.
H NMR (90 MHz, C6D6): ~ 5 03, 4.54 (broad, Si_, ].H)
1.23, 0.88 (SiCH3NI-I)
0.24 (broad, SiC_3, and
'~ SiC_2, 8.3H, for
the total area of SiCH3,
SiC_2 and SiCH3N_)
Molecular weight (cryoscopic in benzene): 1670 g/mol.
TGA (25-1000C, 10C/min): 80% yield of a black ceramic
solid Tl/2 - 610C-
~263796
-56-
Me]ting point (sealed capillary under vacuum): SoEten at
235C, melts at 260C, no further change up to 275C.
b. Usin~ CYC10 ~Cil3SillNH~m Prepared Erom Tlll~.
i. Polvcarbosilane/~CH3SiHNHlm in 1:1 wei~ht
ratio (III-40).
In a dry box, a 250 ml round-bottomed flask equipped with a
stir-bar, reflux condensor ancl a serum cap WAa chnr~ed wlth 0.15
g oE Kll (3.75 m~ol). Tl-IF (50 ml) was added to suspend the Ktl.
A separate 250 ml Schlenk flask was charged with 5.0 g of
ICH3SillNH]m (0.085 mol), prepared in THF solution, and 5.0 g
of polycarbosilane, and 150 ml of THF. The mixed polymer
solution was transferred by cannula into the K}l suspension. The
reaction mixture gradually turned clear and hydrogen gas slowly
~: evolved. The resulting solution was stirred at room temperature
for 24 hours and then 0.5 ml (7.9 mmol) of CH3I was added and
the mixture was refluxed for 2 hours. The solvent was removed
by trap-to-trap distillation. The product was extracted with
200 ml of hexane snd the insoluble residue removed by
centrifugation. The clear, colorless supernatant layer was
transferred via a cannula into a weighed 250 ml round~bottomed
flask. The hexane was removed by trap-to-trap distillation
leaving 9.8 g (98% yield by weight) of a white powder. The
white powder is soluble in THF, benzene, and hexane.
H NMR (90 MHæ, C6D6): ~ 5.21, 4.57 (broad, SiH, lH)
~;~ 1.25 (broad, SiCH3NH)
~ 0.34, 0.30 (broad, SiC_3,
and SiCH2, 8.8H,
for the total area of SiCH3,
SiC_2 and SiCH3N_).
Molecular weight (cryoscopic in benzene): 2560 g/mol.
. ~
lZ63796
-57-
TGA (25-1000C, 10C/min): 86~ yield of a black ceramic
solid Tl/2 ~ 670C.
Melting point (sealed capillary under vacuum): Does not melt at
temperature up to 320C.
Analysis: Found: C, 31.04; Il, 7.36; Si, 50.16; N, 11.62
Total: 100.18%
Ceramic Analysis: Large scale pyrolysis of the sample under
argon gave a 78% yield of a black ceramic solid (25-1000C,
10C/min)
Found: C, 23.36; H, 0.85; Si, 59.95; N, 15.94
Total: 100.10%.
Composition: lSiC + 0.2 Si3N4 + 0.5 C
(equivalent to 7.9 weight % of free carbon)
ii. Polvcarbosilane/~C113~ 3 in 5:1 wei~ht
ratio (III-58).
According to the procedure described previously, the
reaction between 0.05 g of KH (1.25 mmol), 1.0 g of
[CH3SiHNH]m (prepared in THF solution), and 5.0 g of
polycarbosilane was carried out under nitrogen. The resulting
reaction mixture also gradually turned clear with slow evolution
of hydrogen gas. The solution was stirred at room temperature
for 14 hours and 0.5 ml (7.9 mmol) of CH3I was added and the
mixture was refluxed for 2 hours. Work-up as described in the
previous experiment left a white solid (5.9 g, 98~ yield by
weight). The white powder is soluble in THF, benzene, and
hexane.
11 NMR (90 MHz, C6D6): ~ 5.07,4.55 (broad, SiH, lH)
1.24, 0.88 (SiCH3NH)
0.28 (broad, SiCH3,
and SiC_2, 8.1H, for
the total area of SiC_3,
SiCH2 and SiCH3NH).
~Z63796
-5~-
Molecular weight (cryoscopic in benzene): 1100 g/mol
TGA ~25-1000C, 10C/min): 66~ yield of a black ceramic
solid Tl/2 - 530 C.
Meltlng polnt (sealed capillAry un~er vacuum): Softens at
240C, rnelcs at 260~C, no further change up to 275C.
eaction of th Orgallosilicon Comvound with Partially
Del:~ro_ nated Polymerizatioll ~roduct oE
Cyclo-~(CII3)2SiNIIl~n.
o]ylneri7A~on oL Cvclo-i(CII3)2SiNIllm.
~ 100 ml, three-necked, round-bottome~ Elask equipped with a
stir-bar, a thermometer, and two gas inlet tubes was charged
with 45.0 ml (41.4 g, 0.188 mol) of [(CH3)2SiNII]3 and 2.07
g (0.052 mol, 5~ by weight) oE NH4Br. After flushing the
system with nitrogen, a constant stream of nitrogen was
maintained. The reaction mixture was then lleated at 160C for
8 hours during which time N~13 gas slowly evolved. The
reaction mixture was allowed to cool to room temperature, and
then dissolved in 300 ml of diethyl ether. The solution was
cannulated into a 500 ml, three-necked, round-bottomed flask
equipped with a cold condenser (dry ice-acetone) and two no-air
rubber serum caps. The solution was cooled to 0C. An excess
of anhydrous ammonia was bubbled into the reaction mixture
during about 1 hour. The reaction mixture was filtered with a
Schlenk fr'tted filter. The solvent was removed by trap-to-trap
distilLation to leave a viscous oil. The latter was then
distilled under reduced pressure (0.05 mmHg) and the low boiling
compounds ~starting material and oligomers) were collected from
100C to 250C. A very viscous gum remained (20.2 g, 49~ by
weight).
H N~R (90 MHz, C6D6): ~ 0.42 (broad, SiCH3, lH)
0.23 (broad, SiCH3, 1.2H)
~Z63796
-59-
Molecular weight (cryoscopic in benzene): 5100 g/mol.
TGA (25-1000C, 10C/min): 100~ weight loss occurred at
630C.
2. Reaction of Metallated Polymer from Sectlon F.(l) with
~(C}13SiH~x(CH3Si)yln (IV-40~
In a dry box, a lO0 ml round-bottomed flask equipped with a
stir-bar, reflux condenser and a serum cap was charged with 0.1
g (2.25 ~mnol) o~ ~I (5~ by weigllt). TIIF (lO ml) was added to
suspend the KH. A solution of the polymer from L.a. (above)
(2.0 g in 30 ml of THF) was added to the flask by cannulation.
After the addition was finished, the reaction mixture was heated
at reflux for 1.5 hours. The solution gradually turned clear
while H2 gas was slowly evolved.
A separate lO0 ml round-bottomed flask equipped with a
septum, reflux condenser and stir-bar was charged with 2.2 g of
[(CH3SiH~X(CH3Si)y]n (x-0.81, y=0.19). TIIF (30 ml)
was added by syringe to give a clear solution. The KH/polymer
product solution of Section L.a. previously described was
cannulated slowly into the raction flask. Addition of each drop
resulted in formation of an orange color which quickly
disappeared. To the resulting solutlon 0.5 ml (7.9 mmol) of
CH3I was added and the solvent was removed by trap-to-trap
distillation. The product was extracted with 80 ml oE hexane
and the insoluble residue removed by centrifugation. The hexane
was removed from the supernatant solution by trap-to-trap
distillation, leaving 3.6 g (89% yield by weight) of a white
solid. The polymer is very soluble in hexane, benzene, and T}IF.
11 NMR (90 MHz, C6D6):~ 5.12, 4.68, 4.09 (broad, SiH,
1 H)
1.17 (broad, NH) 0.47, 0.27 (broad,
SiC_3, 17.5 H, for the total area
of SiCH3 and N_)
lZ6~796
-60-
Molecular weight (cryoscopic in benzene): 1500 g/mol
Pyrolysis of this polymer to 1000C left a black ceramic
material.
3. Reaction of the Polycarbosilarle with the Product of
Section F.(l).
In a dry box, a 100 ml round-bottomed flask equipped with a
stir-bar, reflux condenser and a serum cap was charged with 0.1
g (2.25 mmol) of ~l (5% by weight). THF (10 ml) was added to
suspend the KH. A solution of the polymer prepared in Section
(a) above (2.0 g in 30 ml of THF) was added into the flask by
cannulation. After the additLon was finished, the reaction
mixture was heated at reflux temperature for 2 hours. The
solution gradually turned clear while H2 gas slowly evolved,
forming the polysilylamide.
A separate 100 ml round-bottomed flask equipped with a
septum, reflux condenser and stir-bar was charged with 2.0 g of
polycarbosilane. THF (30 ml) was added by syringe to give a
clear solution. The polysilylamide solution was cannulated
slowly into the reaction flask. The reaction mixture was then
heated at reflux for 4 hours. The resulting yellow solution was
treated with 0.5 ml (7.9 mmol) of CH3I, the mixture was
refluxed for 2 hours and the solvent was removed by t~ap-to-trap
distillation. The product was extracted with 80 ml of hexane
and th~ insoluble residue removed by centrifugation. The hexane
was removed from the supernatant solution by trap-to-trap
~_ distillation, leaving 3.7 g (93% yield by weight) of a white
solid. The polymer is very soluble in hexane, benzene, and THF.
lH NMR (90 MHz, C6D6) ~ 4.60 (broad, SiH, lH)
0.43, 0.33, 0.23, 0.16, 0.13,
0.11 (multiplet, SiCH3,
SiC_2, and NH, 13.8H, for the
~i3796
-61-
total area oE SiC_3, SiCH2, and
N_).
Molecular weight (cryoscopic in ben~ene): 1570 g/mol.
~yrolysis (to 1000C) gave a black ceramic material.
G. Reactions of ~(C113SillNtl)a(CH3SiN)b-
(CH3SiHNK)Clm Livin~ PolYmer-with-Polvcarbosilane
MiCH~ CH3Siyl_ Or~anopo 1YS ilane
1. Polycarbosilanbe/OrganopolYsilane,/PolYmeric
Silylamide in l:l:2 Weight Ratio.
a. PolYcarbosilane/Polysilane Mixture Added to
~he Polymeric SilYlamide Solution.
A 250 ml round-bottomed flask equipped with a stir-bar,
reflux condensor and a serum c~p was charged wi~h 0.13 g (3.25
mmol) of KH (4.3 mol ~, based on (CH3SiHNH) unit). THF (50
ml) was added to suspend the ~1. Then 5.15 g (0.088 mol of
CH3SiHNH unit) of (CH3SiHNH)moligomer (via ammonolysis of
CH3SiHCl2 in the THF) in 75 ml of THF was added. A vigorous
reaction occurred with brisk evolution of 112. ~fter the
addition was completed, the reaction mixture was stirred at room
temperature for 2 hours.
A separate 250 ml flask equipped as above was charged with
2.58 g of the polycarbosilane and 2.58 g of
l(CH3Sill)x(CH3Si)y]1l (liquid polysilane, preparcd by
sodium condensation of CH3SiHCl2 in 7:l hexane/THF) and 50
ml of THF. To the resulting clear solution was added very
slowly by cannula the polymeric silylamide solution prepared
above. The resulting clear orange solution was stirred at room
temperature for 2 hours and then at reflux for 24 hours.
Subsequently, 0.5 ml of CH3I was added, the mixture was
refluxed for 2 hours and then the solvent was removed at reduced
pressure. To the residue was added 150 ml of hexane to extract
~63796
-62-
the product. Centrifugation removed insoluble salts. The
hexane extracts were evaporated at reduced pressure, leaving
9.12 g (89~ yield, by weight) of a white solid which was Eound
to be soluble in hexane, benzene and THF.
H NMR (90 MHz, CDC13): ~ 5.18, 4.67 (broad, SiH, 1 H)
1.39, 1.22 (SiCH3NH)
0.48, 0.27 (broad, SiCH3
and SiCH2, 6.2H for total
SiC_3, SiCH2 and SiCH3NH)
Molecular weight (cryoscopic in benzene): 1730 g/mol
TGA (25-1000C, 10C/min): 86% yield of a black ceramic
solid,
T1~2=630C
Melting point (sealed capillary under vacuum): does not melt
up to 300C.
Ceramic analysis: Large scale pyrolysis oE the sample under
argon (25-1000C, 10C/min): 77~ yield of a black ceramic
~olid.
b. Alternate Mode of Addition
A solution of [CH3SiHNH)a(CH3SiN)b-
(CH3SiHNK)C]m (prepared by reaction of 0.12.g (3.0 mmol)
of KH and 5.27 g (0.090 mol of (CH3SiHNH) unit) of the
CH3SilIC12 ammonolysis product (prepared in THF) in 50 ml of
THF was cannulated into a 250 ml flask containing 2.63 g of
[(CH3SiH)X(CH3Si)y]n polysilane in 50 ml of THF. The
resulting clear orange solution was stirred under nitrogen at
room temperature for one hour. To this solution then was added
2.63 g of the polycarbosilane in 50 ml of THF. This reaction
mixture was stirred at room temperature for 2 hours and at
reflux for 24 hours. After addition of 0.5 ml of CH3I, the
further procedure followed as described in K.l.(a). The product
polymer was a white, soluble solid (9.14 g, 87~ yield).
~Zçj3796
-63-
H N~R (C6D6): ~ 5.19, 4.72 (broad, Si_, 1 H)
1.39, 0.98 ~SiCH3NH)
0.27 (broad, SiC_3 and
SiC}I2, 5.4H for the total
SiCH3, SiCH2 and SiCH3NH)
Molecular weight: 1790 g/mol
TGA (25-1000C, 10C/min): 85~ yield of a black ceramic
solid.
2. Same ComDonents as in G.(l) in 1:1:1 Wei~ht Ratio
A solution of the polymerl.c silylamide was prepared as
described above (3.20 g oE CH3SlllC12 ammonolysis product,
0.1 g of KH in 100 ml of THF). This solution was added, under
nitrogen wlth stirring, to a mixture of 3.02 g of the
polycarbosilane and 3.08 g of the liquid
[(CH3SiH)X(CH3Si)y]n polysilane in 50 ml of THF. The
further procedure followed that described in G.(l)(a). The
product polymer was isolated as a soluble white solid (8.40 g,
90% yield).
1~ NMR (C6D6): ~ 5.20, 4;81 (broad, SiH, lH)
1.40 (SiCH3N_)
0.47, 0.27 (broad, SiCH3 and
SiC_2, 6.3H for total
SiCH3 SiCH2 and SiCH3NH)
Molecular weight: 970 g/mol
TGA (25-1000C, 10C/mln): 84~ yield of a black ceramic
solid.
Melting point (sealed, evacuated capillary): softens at 310C,
melts 340-350C.
Analysis found: C, 32.64; H, 7.83; N, 9.07; Si, 48.82.
Ceramic analysis: Large scale pyrolysis of sample under argon
(25-1000C): black ceramic in 72% yield.
Analysis found: C, 26.15; N, 12.37; Si, 61.48.
1263796
-64-
Composition: lSiC -1- 0.14 Si3N~ 0./13C
3. Same Components as in G.(l) in 1;2:1 Wei~ht Ratio
A solution of the polymeric silylamide was prepared as
described in G.(l)(a) (3.0 g of CH3SiHC12 ammonolysis
product, 0.1 g of ~-l in 100 ml of TIIF). This solution was
cannulated, slowly with stirring under nitrogen, to a mixture of
3.0 g of the polyc~rbosilane and 6.0 g of the
[(CH3siH)x(cH3si)y]n liquid polysilane in 50 ml of
THF. The further procedure followed that described in K.l.(a).
The white, solid product pol.ylner wns obta:Lned in 92% yi.eld (11.l
g). It was found to be very soluble in hexane, benzene and TlIF.
~1 NMR (C6D6): ~ 5.12, 4.79, 4.19(broad SiH, lH)
1.40 (SiCH3N_)
0.30, 0.25 (broad, SiCH3 and
.~ . SiCH2, 3.9H for total SiCH3
SiCH2 and SiCH3N~I)
Molecular weight: 615 g/mol.
TGA (25-1000C, 10C/min): 74% yield of a black solid.
Melting point: ~sealed evacuated capillary): softens at
230C
melts at 260-270C.
Ceramic analysis: ~arge scale pyrolysis of sample under argon
(25-1000C); 74% yield of a black ceramic.
Analysis found: C, 26.60; N, 8.23; Si, 65.17.
Compositon: lSiC + 0.08 Si3N4 ~ 0.18 C.
, ,
H. Physical Blends
1. Experiments with Polymer Blends
(a) ~(CH3SiH)x(CH3Si) ln/~(CH3SiHNH~a
(cH3~iN)bTcH3~iHN~H3)clm
Blend Prepared at Room Temperature
~2~3796
-65-
In a dry box, 1.1 g (0.025 mol) of
[(CH3Sill)x(CH3Si)y]n (x ~ 0.~6, y ~ 0.54) (Tl-IF
preparation) and 1.45 g (0.025 mol) of [(CH3SiHNH)o 39 -
(CH3SiH)o 61]m (THF preparation) were finely ground
together. The TGA curve of the physical blend polymer was
measured. TGA (25-1000C, 10C/min): 70~ yield of a black
ceramic solid. (average value of the two individual polymers)
(b) A Blend Heated Neat to 100C
In a dry box, 1.1 g (0.025 mo]) of
[(C~l3Si~l)x(Cll3Si)y]n (x - 0.46, y ~ 0.54) and 1.45 g
(0.025 mol) of [(CH3SillNII)0~3g(C~l3SiN)0~61]m (TIIF
preparation) were finely ground together. The solid mixture was
transferred to a 100 ml round-bottomed flask and then was heated
in an oil bath at 100C for 30 minutes. The heat-treated mixed
polymer is insoluble in THF, benzene, and hexane. TGA
(25-1000C, 10C/min): 67% yield of a black ceramic solid.
(c) _ Blend Heated in Toluene at Reflux
The polymer mix~ure prepared ~IS ln ~He pL-ovLous cxperillle
was dissolved in 20 ml of toluene in a 50 ml three-necked,
round-bottomed flask. The solution was heated in reflux for one
hour. The solution ~radually turned cloudy. Solvent was
removed by trap-to-trap distillation to give a white powder
which is insoluble in THF, benzene, and hexane.
TGA (25-1000C, 10/min): 75% yield of a black ceramic solid.
2. Experiments with Phvsical Polvmer Blends of
Polvcarbosilane and
~CH3SiHNH~a(CH3SiN)b(CH3SiHNCH3)Clm.
a. ~sing
~ (cH3siHNH~a~!3siN)b~3siHNcH3)clm
Prepared in Ether SoIution (IV-Z0~.
~Z6~79~
-66-
1. At Room Tem~erature.
In a dry box, 1.0 g of polycarbosilane and 1.0 g oE
[( 3Si}lNH)a(cll3siN)b(cH3siHNc~l3)c]m were finely
ground together. The TGA curve of the physical blend polymer
was measured.
TGA (25-1000C, 10C/min): 76% of a black ceramic solid.
The solid polymer blend was then dissolved in hexane. The
solvent was slowly removed by trap-to-trap distillation to give
a homogeneous mixture. The TGA curve oE the mixture was again
measured.
TGA (25-1000C, 10C/min): 78~ of a black ceramic solid.
ii. At Refluxin~ Toluene Temperature.
The mixed polymer prepared as in the previous experiment was
dissolved in 10 ml of toluene and added to a 50 ml three-necked,
round-bottomed flask. The solution was heated at reflux for 3
hours and the solution remained clear. Solvent was removed by
trap-to-trap distillation to give a white powder which is
soluble in THF, benzene, and hexane.
TGA (25-1000C, 10C/min): 79% of a black ceramic solid.
iii. A Blend }leated Neat at 200C.
The polymer prepared as in the previous experiment was
transferred to a 50 ml round-bottomed flask and was then heated
in a sand bath at 200C for 2 hours. The finely ground powder
turned to a foamy solid at the end of heating. The heat-treated
mixed polymer is insoluble in THF, benzene, and hexane.
TGA (25-1000C, 20C/min): 82% of a black ceramic solid.
Using the same general procedure as outlined above, the
polymer blends between polycarbosilane with different quantities
of [(cH3siHNH)a(cH3siN)b(cH3siHNcH3)c]m (ether
'~ Z63796
-67-
preparation) were prepared. The ceramic yields of these polymer
blends produced are tabulated in Table 7.
b. Usin~
~C113SiltNll~atCI-13SiN)b(Cl135illNc113)clm--
Prepared in THF Solutio-n (IV-27).
i. At Room Tem~erature.
In a dry box, 1.0 g of polycarbosilane and 1.0 g of
[(C~3siHNll)a(cH3siN)l~(cl13sillNcll3)clm were finely
ground together. The TGA curve oE the physical blend polymer
was measured.
TGA (25-1000C, 10C/min): 77~ of a black ceramic solid.
The solid polymer blend then was dissolved in hexane. The
solvent was slowly removed by trap-to-trap distillation to give
a homogeneous mixture. The TGA curve of the mixture was again
measured.
TGA (25-1000C, 10C/min): 80~ of a black ceramic solid.
ii. At Refluxin~ Toluene Temperature.
The mixed polymer prepared as in the previous experiment was
dissolved in 10 ml of toluene and added to a 50 ml three-necked,
round-bottomed flask. The solution was heated at reflux for 3
hours and the solution remained clear. Solvent was removed by
trap-to-trap distillation to give a white powder which is
soluble in THF, benzene, and hexane.
TGA (25-1000C, 10C/min): 76% of a black ceramic solid.
~_,
iii. A Blend Heated Neat at 200C.
The polymer blend prepared as in the previous experiment was
transferred to a 100 ml round-bottomed flask and was then heated
in a sand bath at 200C for 2 hours. The heat- treated mixed
~2~3796
-68-
polymer is insoluble in THF, benzene, and hexane.
TGA (25-1000C, 10C/min): 86~ of a black ceramic solid.
Using the same general procedure as outlined above, the
polymer blends between polycarbosilane with diEferent quantities
of [(CH3SiHNH)a(CH35iN)b(cH3si~lNcH3)c]m (THF
preparation) were prepared. The ceramic yield of these polymer
blends produced are tabulated in Table 7.
c. Ternarv Blends
i. Mixed at ~oom Temperature
In a dry box, 2.0 g of the polycarbosilane, 2.0 g of the
liquid [(CH3SiH)X(CH3Si)y]n oreanopolysilane and 4.0
of the l(CH3SiHNH)a(CH3SiN)b(CH3SiHNCH3)C]m
polysilazane (prepared in THF solution) were combined to give a
nonhomogeneous mixture which was dissolved in 40 ml of hexane.
This solution was stirred at room temperature for one hour and
~LZ63796
--69--
~ t~ ~ W. ~ W~ ~
~h t~ tc~ ; .
O ~r @ ~ ( n n ~ ~ a
~ ~ ~ r~ D * K:
~r
wQ wQ w~ w
_ o
~_,, I ~ o
j.~
~Z63796
-70-
then was evaporated at reduced pressure. A homogeneous white
powder remained. This material was Einely ground under nitrogen
and examined by thermal analysis. TGA (25-1000C,
10C/min): 77~ yield of a black ceramic.
ii. At Refluxin~ Toluene Temperature
The polymer mixture prepared in L.3.(a) was dissolved in 40
ml of toluene in a 100 ml flask equipped with a reflux condenser
and a nitrogen inlet tube. The solution was heated at reflux
under nitrogen for 3 hours. Subsequent removal of solvent at
reduced pressure left a white powder which was soluble in
hexane, benzene and THF. The powder was finely ground and
examined by thermal analysis.
TGA (25-1000C, 10C/min): 76% yield of a black ceramic.
iil. Neat at 200
In a dry box 4 g of the polymer blend prepared in
H.(2)(c)(i) was charged into a 250 ml flask equipped with a
reflux condenser and a nitrogen inlet tube. The flask was
heated in a sand bath at 200C for 2 hours. The resulting
hard, solid product now was insoluble in hexane, benzene and
THF. It was finely ground and examined by thermal analysis.
TGA (25-1000C, 10C/,min): 85~ yield of a black ceramic.
I. Ceramic Preparations
-- 1. Or~anopolysilane-derived Ceramic Preparations
a. Preparation of Ceramic Fibers
i. From Mixed Polvmer Prepared as in Example D.(l)(a)(i)
(a)
In a dry box, an approximately 1 g sample o$ the polymer was
dissolved in toluene (ca. 10 ml). The solution was concentrated
~Z6~79~
under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 foot long were pulled with a glass rod
dipped into the gummy mass. The fibers were quickly placed in a
fused silica crucible which was in turn placed in a quartz tube
in a tube furnace and flushed with nitrogen. The polymer fibers
then were pyrolyzed at 10C/mln to lOOO^C. Thls produced black
ceramic fibers.
ii. From Mixed Polymer Prepared as ln Example D.tl)(b)(ii)
(b)
The same procedure was used in preparation Or polymer fibers
in this polymer. The fibers were quickly placed in a fused
silica crucible which was in turn placed in a quartz tube in a
tube furnace and flushed with nitrogen. The polymer fibers then
were pyrolyzed at 10C/min to 1000C. This produced black
ceramic fibers.
b. Preparation of Ceramic Bars bv Polymer PyrolYsis
The two organosilicon polymers used for these experiments
were prepared as described earlier.
i. Mixed Polymer Prepared as in Example D.(l)(a)(ii)
The polymer (3.0 g) was loaded into a 3.9 cm x 1.3 cm x 3.7
cm rectangular steel die and uniaxially pressed at 5000 lbs. for
5 minutes. The polymer bar was then bagged and isostatically
pressed at 40,000 psi for one minute. The sample was placed in
a quartz tube in a tube furnace and pyrolyzed under nitrogen to
1000C, heating at 10C/min. A black, irregular-shaped foam
product was obtained with a loss of 24~ of the original weight.
ii. Mixed Polymer Prepared as in Example D.(l)(a)(ii)
~,Z63796
-72-
The polymer bar (3.0 g) was prepared by the same procedures
used in the preparation of polymer bar above. The polymer bar
was placed in a quartz tube in a tube furnace and pyrolyzed
under nitrogen to 1000C, heating At 10C/min. A black,
irregular-shaped foam product was obtained with a loss of 26% oE
the original weight.
c. Preparation of SiC Powder Composites
i. Mlxed Polymer Prepared as in Example D.(l)(a)(l)
In a dry box, 2.4 g of fine -SiC powder and 0.6 g (20~ by
weight) of mixed polymer were combined in a 100 ml
round-bottomed flask. The flask was removed from the dry box,
charged with 10 ml of toluene, and the ceramic powder was
dispersed ultrasonically for one hour. The toluene was removed
on a rotary evaporator and the ceramic powder/polymer residue
was further dried under vacuum for about 30 minutes. The
residue was removed from the flask and lightly ~round in a
mortar and pestle to produce a fine powder. The powde~ were
loaded into a 3.9 cm x 1.3 cm x 3.7 cm rectangular steel die and
uniaxially pressed at 5000 lbs for 5 minutes. The bar of
ceramic powder was then bagged and isostatically pressed at
40,000 psi for one minute. The sample was placed in a quartz
tube in a tube furnace and pyrolyzed under nitrogen to 1000C
heating at 10C/min. A slightly shrunk ceramic product was
formed with a loss of 6% of the original weight.
ii. Mixed Polymer Prepared as in Example D.(l)(a)(ii~
In a dry box, 2.4 g of fine -SiC powder and 0.6 g (20% by
weight) of mixed polymer were combined in a 100 ml
round-bottomed flask. The flask was removed from the dry box,
char~ed with 10 ml of toluene, and the ceramic powder was
1263~96
-73-
dispersed ultrasonically for one hour. The toluene was removed
on a rotary evaporator leaving a gray residue. The ceramic
powder/polymer was further dried under vacuum for about 30
minutes The residue was removed from the flask and lightly
ground with a mortar and pestle to produce a fine powder. The
powder were loaded into a 3.9 cm x 1.3 cm x 3.7 cm rectangular
steel die and unlaxlally pressed at 5000 lbs for 5 minutes. The
bar of cernmic powder was then bagged and isostatically pressed
at 40,000 psi for one minute. The sample wa.s placed in a quartz
tube in a tube furnace and pyrolyzed under nitrogen to lOOO~C,
heating at 10C/min. A slightly shrunk ceramic product was
formed with a loss of 6% of the original weight.
This invention has been described in detail with reference
to the preferred embodiments thereof. However, it will be
appreciated that those skilled in the art, upon consideration oE
this disclosure, may make modifications and improvements without
departing from the spirit and scope of the invention as
described in the claims.
2. PolYcarbosilane-derived Ceramic
a. PreDaration of Ceramic Fibers.
i. From Mixed Polvmer Prepared as in D.(3~(a~(i)
In a dry box, approximately 1 g of sample III-37 was
dissolved in toluene (ca. 10 ml). The solution was concentrated
under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 ft long were pulled with a glass rod
dipped into the gummy solid. The fibers were quickly placed in
a fused silica crucible which was in turn placed in a quartz
tube furnace and flushed with argon. The polymer fibers then
were converted into ceramics by pyrolyzing them at 10C/min to
~Z63796
-7~-
1000C. This produced black ceramic fibers. S~M micrographs
of the ceramic fibers were obtained.
ii. From Mixed Polvmer Prepared as in D.(4)(a)(i)
In a dry box, approximately 1 g of sample III-39 was
dissolved in toluene (ca. 10 ml). The solution was concentrated
under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 ft long were pulled with a glass rod
dipped into the gummy solid. The fibers were quickly placed in
a Eused silica crucible which was in turn placed in a quartz
tube furnace and flushed with argon. The polymer fibers then
were converted into ceramics by pyrolyzing them at 10C/min to
1000C.
This produced black ceramic fibers. SEM micrograpl-s of the
ceramic fibers were obtained.
iii. From Mixed Polvmer Prepared as in D.(3)(a~
In a dry box, approximately 1 g of sample III-40 was
dissolved in toluene (ca. 10 ml). The solution was concentrated
under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 ft long were pulled with a glass rod
dipped into the gummy solid. The fibers were quickly placed in
a fused silica crucible which was in turn placed i.n a quartz
tube furnace and flushed with argon. The polymer fibers then
were converted into ceramics by pyrolyzing them at 10C/min to
1000C. This produced black ceramic fibers. S~M micrographs
of the ceramic fibers were obtained.
b. Preparation of Ceramic Bars.
i. From Mixed Polvmer Prepared as in D.(3~(a)(i~.
The polymer (III-37, 2.28 g) was loaded into a 3.9 cm x 1.3
~;263796
-75-
cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000
lbs for 5 minutes, The polymer bar was thetl bagged and
isostatically pressed at 40,000 psi for one minute, The sample
was placed in the quartz tube furnace and pyrolyzed under argon
to 1000C, heating at 10C/min, A black, rectangular-shaped
bar was obtained with a loss of 32% of the original weight. SEM
micrographs of the ceramic bar was obtained,
ii. From Mixed Polymer Prepared as in D.(3)(b~(i).
The polymer (III-38, 2,57 g) was loaded into a 3,9 cm x 1.3
cm x 3,7 cm rectangular steel die and uniaxially pressed at 5000
lbs Eor 5 minutes, The poLymer bar w~s thell bagge<l and
isostatically pressed at 40,000 psi for one minute. The sample
was placed in the quartz tube furnace and pyrolyzed under argon
to 1000C, heating at 10C/min, A black, rectangu].ar shaped
bar was obtained with a loss of 29% of the original weight, SEM
micrographs of the ceramic bar was obtained,
iii, From Mixed Polymer Prepared as in E,(2)(a~
The polymer (III-39, 2,36 g) was loaded into a 3.9 cm x 1,3
cm x 3,7 cm rectangular steel die and uniaxially pressed at 5000
lbs for 5 minutes. The polymer bar was then bagged and
isostatically pressed at 40,000 psi for one minute. The sample
was placed in the quartz tube furnace and pyrolyzed under argon
to 1000C, heatlng at 10C/min. A black, rectangular shaped
bar was obtained with a loss of 27~ of the original weight, SEM
micrographs of the ceramic bar was obtained,
iv. From Mixed Polymer Prepared as in E.(2)(b)(i).
The polymer (III-40, 2,07 g~ was loaded into a 3,9 cm x 1.3
cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000
~.Z6~3796
-76-
lbs for 5 minutes. The polymer bar was then bagged and
lsostatically pressed at 40,000 psi for one minute. The sample
was placed in the ~uartz tube furnace and pyrolyzed under argon
to 1000C, heating at 10C/min A black, rectangular shaped
bar was obtained with a loss of 24~ of the original weight. SEM
micrographs of the ceramic bar was obtained.
This invention has been described in detail including the
preferred embodiments thereof. ~owever, it will be appreciated
that those skilled in the art, upon consideration of this
disclosure, may make modificatlons and improvements without
departing fro~ the spirit and scope of the invention as set
forth ln the claims.
.
