Note: Descriptions are shown in the official language in which they were submitted.
7~
This application is a division oE co-pending
Canadian Patent Application, serial no. 545,027 filed
August 21, 1987 and entitled M~THOD FOR USING
ORGANOPOLYSILAZANE PRECURSORS T() FORM NEW PRECERAMIC
POLYMERS AND SILICON NITRIDE-RICH CERAMIC MA~ERIALS.
The present invention relates to a process for
preparing silicon-containing preceramic polymers that is
particularly useful for making silicon nitride and silicon
nitride/silicon carhide and silicon oxynitride 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, silicon oxynitride and other
silicon-based ceramic materials. R.W. Rice, Amer, Ceram.
SOG . BU11 ., 62 ; 889-B92 (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
~ ,,
~JS~";
-- 1 --
4~5
liquid) or by a solutlon of ehe polymer, with ~ubsaqu~nt pyrolysi~ to
for~ a cera~ic, resulting in b0tt~r str~ngth, oxldation rasistance,
etc., of the body; and
6. ~ormation of thin films of thc ceraMlc Msterial for
elactronics appllcatlon~.
For lnstance, Penn ~t al., ~ es,~ 3751-61
(19S2) describe thc preparation of silicon carbide~sllicon nltride
fibers irom a polycarbosilaYane precursor. Tr~s(N-methylamino)
methylsilane monomer was formed by reaction of monomethylamine and
methyltrichloros$1ane in dry p~troleum ether and a polycarbo~ilazane
resln was formed by passing the monomer over glass Raschig rings at
520C. The brlttle polymer was soluble in methylene chloride and
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 hava been described in U.S. Pat. Nos. 3,108,985;
3,353,S67; 3,892,583; 4,310,651 and 4,312,970. Ihesa linear or
crosslinked polymers and processes for producing ceram~c materials
have generally been found to be deficient in one or ~ore ways.
S. Ya~ima, ~ C~ c ~L , 6?: 893-898; 903 (1983)
discloses using (CH3)2SiCl2 as a qtarting materisl for a
preceramic poly~er for tha preparation of S~C-containin~ caramics.
The polymer of Ya~im~ is prepared by ~odium metal condensation of
(CH3)2SiCl2 to re~ult in a poly~ilanc, -[(C~3)2Si]n- ~n
i9 approximately 30). Thic polysilan0 can then for~ either a "Mark
I" poly~er or a ~ark III" polym~r dependin~ upon tha treatmeat
used. Heating in an autoclave under argon at 100 kPa at
450V-470C for 14 hours results In a Mark I polymer while adding
a few pcrcent of a polyborodiphenylsiloxane and h~ating under
nitrogan at ambient pressure at 350C for 10 hours results in the
Mark III poly~er. In either case, the polysilicon backbone is
-2-
L~ 7~
convarte~ to a poly~arlc chain in which the main repeat unit is:
CH3
I-li-CH~
Ths Mark I polymer also contains ~ome -[(CH3~2SiCH2]- unlts. Th~
Mark III polymer contain~ so~c Si-Si bondq in the form
-[(C~3~2Si-Si(CH3)2ln((n 2-8) units and a low p~rcen~age oi
[(C6H5)2SiO] units~ These preceramic polymers can be processsd
to glve ceramic flbers contalning SiC, soms free carbon and some
SiO2. Howevsr, there are problems assoclated with these
polycarbosilane-deri~ed ceramlcs. They have a tendency to crystallize
below 1200C, they have a SiO2 content as a result of an oxidativa
cure step, and free carbon and a relatively low cer~mic yield is
obtained upon the$r pyrolys~s for a com~ercial product. ~hile the
ceram~c yield for the Mark III polymer i 68%, the yield for the Mark I
polymer is only 54~.
Silicon oxyni~rides are another i~portant group of ceramic~. This
ceramic material has most of the same advantages as sllicon nitride,
but is exper-ted to have a better oxidation stability. These are h~gh
re~ractory matarials able to withstand t~mperatureq up to about
1500C before decomposing. Although K. Okamura at al, Çhe~. Let~.
(1984): 2059-2060 (See also K. Oka~ura et ~l, Fi~th Int. Con~. on
L ~9 ~ L~ , July 29 - Augu~t 1, 1985, ProcQedings: 53S-542),
reported obt~ining silicon oxynitrid~ fibers after pyrolysis under
ammonia, of SiQ2-containing polycarbosilan2s (having
[CH35i(H~CH2J as the ma~or rspeat unit3, this WRs an expensive and
inefficient process.
U.S. Pstent 4,482,669 issued Novembar 13, 1984, describes
organopolysilazane preceramic poly~ers whose pyrolysis gives a mixture
of silicon carbide and ~ilicon nitrlde wherein, generally, neither
component is in large excass over the other. Th~se polymers were
obtained by the reaction of a base (such as an alkali metal hydride,
amide, etc.) with the = onolysis product of a dihalosilane, for
-3-
14 7~;
~xflmplo, CH3SlHC12 which r~sults in a poly~arlz~tion procas3bcliQved to lnclude the ~çhY~rocY~lodim~riz~ion (DHCD) reAction ~hown
in cq. A.
base / N
2 -~i.7~ 2 H~ ~ /si Si ~ (A)
H H \ N
The action of a caealytic ~mount of the bsse on thssa cyclic
oligomers l$nks them togeth0r via such cyclodi~ilazan~ units into 8
sheet-llke array. Treatment of, for example, the CH3SiHC12
ammonolysis product by th~ base, usually KH (9.5-4 mol perc~nt based
on CH3SiHNH units), pro~idP~ a polysilazane lntermediate of type
[~CH3SiHN~)a(CH3SiN)b~CH3SiHNK)C~n, l.e. a "living~
polymer which still contains reactlve silylamide functions. This
"living" poly~llazane intermedlate c~n bc tr~sted with a suitabla
slectrophil~, such a~ C~3I or a chloro~ n~, to "n~tralizs" the
reactive ~ilylamide functions. Ultimat~ly, on pyrolysis in an inert
gas s~ream ~N2 or Ar) to 1000C, the yield of ceramic r2sidu~ is
high (80-85~. A typical composition of such ~ cer~mic material is
0.9 Si3N4 ~ 1.3 SiC + 0.75 C or, on a weight ~ basls, 67%
Si3N4, 28~ SiC and 5~ C.
U.S. Patent Applicaelon Serial ~o~. 756,353, fil0d July lR, 198~,
and 781,934, filed Septemb~r 30, 1985 describe methods for converting
organosillcon polymers contatning SL-H repeat units to ne~ and u~eful
preceramic poly~ers and ceramic materials. The prec~ramic poly~ers,
which are prepared by reactine elth~r an organopolysilan~ or a
polycarbosilane with a silylamide result in preceramic polymers whose
pyrolysis gives a ~ixture of silicon carbide and silicon nitride
ceramic materisls, which ara ~enerally r~ch in silicon carbide.
It would ba useful to have a polymer precursor that is form~d
from readily available and relatlvely inexpensiv~ startin~ materials,
~hat is stab1e at room temperaturc, ls fusible and/or solublc in
-4-
;
organic solvents and whose pyrulysis can provido a high yield of
cer~ic produc~s. It would also be usaful to b~ abla to have such a
poly~er precursor which forms a cora~ic materi~l upon pyrolysls that
iq rich ln the silicon nitride compon~nt.
Sum~ar~ of Invention
W~ have discovered a method for preparin~ pr~ceramic
organosillcon polymers, where the resultant ceramic materlal i9
generally richer in silicon ni~ride than obtained with the
corresponding dihalosilane alone as initial start~ng ma~erial. The
process comprises the following steps:
(a3 reacting in solution anhydrous ammonia with a mixture of
RlSiHX2 (wher~in Rl ls B lower alkyl group having from 1 to
about 6 ca~bon atoms, a ~ubstituted or unsubstltuted cycloalkyl group
having fro~ 3 to about 6 carbon atoms, a substitutcd or unsubstituted
lower alkenyl group havin~ fro~ ~ to about 6 carbon atoms, or a
substituted or uQsubstituted low~r aryl group having from 6 to about
10 carbo~ atomc, and X is a halogen) and RSiX3 (~h~reln R is H, a
lower alkyl group having from 1 to about 6 carbon atom~, a
substituted or unsubstituted cycloalkyl group ha~ing from 3 to about
6 carbon atoms, os a substituted or unsubstituted lower alkenyl group
ha~ing from 2 to about 6 carbon atoms, or a substituted or
unsubstitut~d lDwar 3ryl ~roup havlng from 6 to about 10 carbon
atoms~ ther~by forming a mixture of precur~or poly~6rs; ant
(b) reacting ~sid pracursor polymer~ in the pr~senc~ of a basic
catalyst capable of daprotonatlng the NH functlons ~n ~aid precursorq
to for~ said preceramic polymer, thereby carrying out the DHCD
reaction. Preferably, the resultant preceramic polymer is treated
wlth an electrophilc compound. In a preferred embodime~t X is Cl,
Rl is a lswer alkyl group and R i H or a lower alkyl group.
The polymer formed by this method can be pyrolyzed in an inert
gas stream to fo~m a black ceramic material. Pyrolysis of a
prsc~ramic poly~er formed wher~ ~1 is a lower alkyl group and R is
lX~ 75
~ or a lower alkyl group under a stream of ammonia results in a
white ceramic material.
Detailed Descript_on of_the Invention
The following description of the inven-tion includes not only
the method for preparing preceramic polymers summarized above,
but also a method comprising reacting a polymeric silylamide with
an organosilicon polymer, which is claimed in co-pending Canadian
Patent Application Serial No. 545,027, of which the present
application is a division.
We have now discovered that by using the coammonolysis product
of a mixture of a dihalosilane and a trihalosilane, one can obtain
a preceramic polymer whose pyrolysis results in a ceramic material
richer in silicon nitride than the polymer obtained by using the
ammonolysis product of the corresponding dihalosilane alone.
4~
Additionally, the co&mmonoly3is product i3 oft0n ~ora soluble than
the ammonolysis produce of the correqpondlng trlh~losil~na, and
because an lwportant rQquire~ent for ~ u~ l precera~ic polymsr is
that it ba proces~ablc, ~. 9 ., fusible, and/or sol~ble in organic
solvent-~, the coam~onoly3is produce i~ preferable.
Preferably, the dihslosilane i~ of th~ formula RlSiNX2,
wherein Rl ls a low~r alkyl group having from 1 to about 6 carbon
ato~s, a substituted or un~ubstituted cycloalkyl group h~ving from 3
to about 6 carbon atom~, a sub~tituted or unsub~tituted lower alkenyl
group having from 2 to about 6 carbon a~oms, .or a substituted or
unsubstituted lower aryl group having from 6 to about 10 carbon
atoms, while X is a halogen, preferably, fluorine, chlorine, bromine
or iodine. More preferably, Rl is a lo~er alkyl group. Host
preferably, Rl is CH3. X is preferably chlorin2.
Prefsrably, the trihalosilane has the formula RSiX3,
wherein R is hydrogen, a lower alkyl group having from 1 to about 6
carbon atoms, a substituted or un~ubstituead cycloalkyl group having
from 3 to aboue 6 carbon atoms, a substituted or unsubstituted lower
alkenyl group having from 2 to about 6 carbon atom~, or a substituted
or unsubstituted lower aryl group havlng from 6 to about 10 carbon
atoms and X i~ a halogen, preferably, fluorine, chlorine, bromine or
iodine. More preferably, R ii 8 hydrogen or ~ lower alkyl group.
Still more preferably R is hydro~en or CH3. ~ost pref~rably, R ls
hydrogsn. X ls preferably chlorine.
The coa~monolysis reaction is carried out in any or~anic sol~ent
ln which the two reactants are soluble. Solvent~ wh$ch may be used
include ethers such as dialkyl ethers, partlcularly dlethyl ether
~Et20); cyclic ethers s~ch a~ tetrahydropyrsn, 1,4-dioxane,
preferably tetrahydrofuran (THF); glycol ather~; aliphatic
hydrocarbons such as pentane, hexane; and aromatic hydrDcarbon~ such
a~ benzene, toluene, xylenes. Oth~r useful solventq ara well known
eo the person of ordinary skill in the art, based upon this
disclosure. The RlSi~X2~RSiX3 ~ixture is then reacted with
ammonia in such a solvent to effece the co~monolysis reaction.
14~
In a prsferred embodimene ~f eh~ prosent i~v~ntion, ehe
coammonolysis product is treatad ~ith catalytic quantltia~ of a base
capable of deprotonating th~ NH function3 in the re~ultant
coam~onoly~ls product, for sxa~Rl0, ~H, in an organie solvont. A
dahydrocycl~dimerl~ation resction (DHCD) tak~s pl~co, whlch re~ults
in a preceramic polym~r that givas high c~ramic yield~ upon
pyrolysis. Preferably, th~ bas~ 19 an alkali metal, an alkali metal
hydr{~e, an alkalin~ earth m~tal hydride, an ~lkali m~tal amids, an
alkaline earth metal amlde, a complex alkali metal hydridc, e.g. XB
(sec-Bu)3H, LlAlH4, etc., alkali and alkaline earth metal
silylamides, an alkall metal organic compound and the like. More
preferably, the base is KH. Only small amounts of the base are
necessary (0.1-10 mole percent based upon the NH containing repaat
unit) because the reaction is catalytic.
The coammonolysis product is reacted with the base in any organic
solvent, in wh$ch the coammonolysi~ produc~ is Qoluble without
raaction. Such organic solvent~ includa sthers, such as dialkyl
~thers, pr~ferably dl~hyl 3ther; cycl$c ~th~r~, for example,
p~eferably, THF; glycol ethers, aliphatic hydrocarbonq such as
alkan~s, ar2nes, and combinations thereof.
The temperature at which this reaction takes plac generally
rang~s ~rom about -10C to about ~30C. Aftes the reaction i9
complete, the mixture may be quenched wieh an electroph$1e, EX,
capabla of reaction w~th residual ~llyla~ide functlons. E is any
organ$c group, praferably, a lower alkyl group or 3ilyl group; ~ is
pref8rably 8 halide, sulfate or sulfonate. The alectrophile can be
an alkyl halide, sulfate or sulfonae~; a hslosilane; or the like.
Typically, CH3I or a chlorosilane is used although other equi~alent
elactrophiles well-known to those skilled in the art csn also be
us~d. This qu~nching limlta ehe reactiYity of th~ "living~ polymer
int~rmediate.
- 8 -
~i4>7S
The precer~ic polymer produced by th~ DHCD re~ctlon typicAlly ls
a wh~te solid, which 1~ produc~d ln virtually qu~ntitatIv~ yleld.
Whsn Rl was CH3, X ~as Cl ~nd R w~s H, the proton MMR spectra of
the products showed ~n incr~a~ Ln the SICH3/SlH ~ NH proton ratio,
while the r21ative SiH/NH ratlo was unchanged. Thls indlc~te~ that a
hydrogen loss had taken plac~.
In the D~CD raaction~, the molecular wei~he of the solid product
was greater th~n that of the starting cosm~onolysis produce, thus a
polymerization rsaction had occurred. The convarsion of the olls
which typically are formed in ehe coa~monolysis reactions to the
solids of the present invention results in a material that is more
easily handled.
Pyrolysis ~f the whit2 solid obtained in these base-cataly~ed,
DHCD reactions under argon fro~ 50 to 950C, typically producPs
black cer~mic residues. The cera~ic yields were generally
excelle~t. These caramic ~atarials have a rich ilicon nitride
coneent.
Relatively pure slllcon nitride material can be for~ed when the
precera~ic poly~er is pyrolyzed in a s~ream of a~onia rather than of
an inert gas such as nltrogen or argon. The ammonia reacts wlth ths
polymer at higher te~peratures to cleave methyl groups from silicon,
so that essentially all carbon ls lost. For exa~ple, where Rl is
CH3 ~nd R ~s H, the pyrolysis of the preceramic polymer derived
f~om the DHCD product of the 1:1 coam~onolysis (in THF~ product to
1000C in a stre&~ of ~mmoni~ produced a ~hit¢ cer~mic resldue in
high yield containing only 0.29~ by weight C, with the remainder
being sillcon nitride. When both Rl and R were CH3, the
pyrolysis of the preceramic polymer derived from the DHCD product of
the 6:1 coammonolysis (in Et20) pro~uct to 1000C in A stream of
2mmonla produced a white ceramic residue containin~ only 0.36~ by
weight of carbon. Si~ilarly, pyrolysis of a 3:1
CH3SiHC12:C2H5SiC13 ~coa~monoly~is product in Et20)
KH-cataly~ed DHCD (in THF) product ~o 1000C in ~ stream of ammonia
produced an essentially pure white residue with a very faint brown
~2~3~4'7~
tinge. How~var, ~lk~nyl groups ~ppeAr ~o b~ ~ore lneim~t~ly involved
wlth eh~ pyrolysi~ ch~mlQtry. Pyroly~1~ of a control n~monolysis
product of CH2-CHSiC13 to 1000C in a 3tr~m of ~monia
produced a brown cer~mic re~idue, while pyrolysl3 of a 3:1
CH3SiHC12:e~2~C~SiC13 (coammonolysis in THF) KH-catalyz~d
DHCD (in THF) product in 8 s~r0am of s~monia produced 8 ceramic that
was bl~ck with touches of white nnd brown.
A wide range of RlSiHX2:RSLX3 raelos can be used in
preparing the coam~onolysis product, the mole ratio can be Eor
ex~mple from about 20:1 to 1:20, it preferably ranges from about 8:1
to 1:7. Generally, the higher the mole ~ of dihalosilane used, the
more soluble is the co~mmonolysis product. However, this product
~enerally forms a ceramlc material in lower yields. In addition, at
a hlgh mole ~ of trihalosil~ne, the DHCD reaction has less effect.
The DHCD reaction at hlgh mole ~ of trihalosilane should be limlted
to the qoluble reaction product. For certain halosilanes, however,
the coammonolysis product obta~ned wlth high levels of trihalosilanP
has properties that are quite use~ul without ~ subsequent DHCD
re&ction. When ~ DHCD reactlon is contemplated, the mole ratio of
RlSiHX2:RSi~3 is preferably from about 8:1 ts about 1:6, more
preferably fr~m about 8:1 to about 1:2, e~en more preferably About
6:1 to about 1:1. A higher mole ratio of dihalosilane to
trihalosilane, such ~s about 6:1 to 3:1, provides ~ coammonolysis
product that 5s typically soluble, which, when subjected to a DHCD
r~ction, ~esults in a preceramic poly~er that provides ex~ellent
yiel.ds o~ ceramic material. No~ever, a ratio ~f about 2:1 to ~:2,
preferably aboue 1:1, produces a preceramic poly~er whose pyrolysis
in an inert atmosphere, typically, resules in a greater percent of
silicon nitride in the ceramlc material than obtained on using the
higher mole ratio of dihalosilane. Thus, depending upon the desired
end product and reaction sequences, the molP ratio of
dihalosilane:trihalosilane will vary. The particular ratio to use in
a given situation can readily be determined empirically by the
dçsired end use based upon the present disclosure.
--10--
47S
For example, = onolysi~ of HSiC13 ~lon~ giVY~ ~o~tly
lnsolublc, highly croYs-link~d product~. The hi8h~t ylold of
soluble products (47%) was obt~ined wh~n the HSiC13 ~m~onolysis was
carried out at -20C (at 0C eh~ yleld of solublQ product wa5
17~, ae -78C it wa9 20~). However, thes~ initially ~oluble
silazanes become insolubl~ ~fter th~ solvent 13 removed. Since th~
main requ~re~ent of a precera~ic poly~er is that lt must be
processabl~, i.e., fusible and/or soluble in organic qolvents,
= onolysis of HSiC13 alone is not satisfactory.
When R is H, and Rl is CH3 nd X is Cl, the pr~ferred ratio
of RlSiHX2:RSiX3 ranges from about 8:1 to about 1:4; more
preferably, the ratio is about ~:1 to about 1:2 when a DHCD reaction
is used; ~ore preferably about 6:1 to about 3:1 when one is concerned
with the solubiliry of the starting materials; and about 3:1 to about
1:2, mor~ preferably about 1:1 when one is Intere~ted ln the
result~nt w~ight percent of the ceramlc residus obtained after
pyrolysis in an inert atmosphere; and 1:1 to about 1:4, most
preferably about i:3 when the coam~onolysi~ product wlthout a DHCD
reaction is desired.
In either Et2O or THF, the 6:1 and 3:1 ratios used in the
coammonolysis produced polysilazane oll~ wieh ~olecular weights in
the ranBe 390-401 g/mol and 480 g/mol, respectively. When Q 1: 1
reactant ratio was used, waxes of so~ewhat higher (764-778 g/~ol)
molecular weights were obtained in both solvents. In the 1:1
react$on carried oue in Et20 the yield of soluble product was only
40~, but in THF it was nearly q~antitative.
The oils produced in the 6:1 and 3: l reactions in Et2O are
stable on long-term storage at room te~perature ln the absence of
moisture (e.g., in an inert atmosphere box). However, the waxy
product of 1:1 reactions in (Et20) and all the co = onolysis
products prepared in THF formed gels (i.e., became insol~ble) after
3-4 weeks at room temperature, even when stored in a nitrogen-filled
dry box. (See Tables 1 and 2).
1~ 8~ 5
~L~L
RQ~
12EI~l)RQ~YÇl,OI)I~
~2 Ccramic
HSlC13 _ Yield by
Re a c t i oT~ ~i e 1 d ( 9~ ~ MU TÇA . %
6 oil 74 390 33
Coammonolys 1~
in Et20 3 oil 79 484 41
wax 40 778 72
. . ~ .
6 so1id 100 1300 85
DHCD Reactl~n,
1~ KH in THF 3 ~lid 99 1250 B8
so1id 53 1630 87
-12~
~2
~__~C~$~
~2 Cer~nic
~SS~C13 Yield
~-'GL tbl~R,qt~o ~rPduct ~ield(~GA~
6 oll 91 401 28
Coa~nmonolysis
ln THF 3 oi l 85 482 67
W8X 94 764 78
6 sol~d 96 10~4 82
: DHCD Reactlon,
1% XH in THF 8 solid 97 942 82
solid 93 1620 B6
--13--
475
The in~gr~t~d proton N~R ~p~ctra of ~h~ various co~mmonolysl
products ~stablish thsir ~25Q$~ QS~ con~tleu~lons:
ÇH~ Ç~ iÇ~3_~1Q~ o~- _
6:1 [CH3Si~NH]1 o[~Si~NH)1.5]0.17
3:1 [CH3SiHNH]l.olNsi(NH)l.5lo.33
1:1 [CH3SiHNH]l.~[HSi~NH)1.530.37
These formul~s carry no ~truc~ural impllcat~ons, they meraly are
average formulstions. The HSiC13 component probably
introduces both SiNHSi brid~ing and SLNH2 ter~inal groups
into the structur~. From these approximate formulas one can
calculate expec~ed ~ C, H, N and Si compositions a~d, in
g~ner~l, the agreement of obs~r~ed ~ C, H and ~ for the 6 :1 ~nd
3:1 products with these values i good (+ 0.55~). (Analyses
were not obtained of the w~x~s prepared in the 1:1 reactions).
The pyrolysis of th~se coammonolysis products was studied.
The 5 CH3Si~C12:1 HSiC13 am~onolysis product gives low
ceramic yields on pyrolysis. Pyrolysis of the 3:1 products
gives increased ceramic yields, whil~ pyrolysls of the ~ost
highly cross - linked 1:1 am~onolysis products glves quite good
cers~lc yields*, 72~ for the product prepared i~ Et20, 78% for
that prepared in THF.
*Ceramic yield ls defined as
weig t of residue _~ 100
weight of sample pyrolyzed
-14-
7~
Sub~cting ~ha3s coam~onoly~is produces to Ch~ DHCD
reaction, using XH as n bAse rc~llt~d in white ~olLd~ in
~lrtually quantitative yield. Th~ solids Ar3 ea~i~r to handle
and store ehsn th~ oil~. Pyroly3i3 of the whiee 9011ds
obtained ln these RH-catalyzed DHCD r~actions (under srgon from
50-950C) produced black cera~ic r~sid~3~, ~ith the exception
of the 1:1 THF ammonolysis-d~rlved sol~ d which left a brown
residue. The ceramic ylelds ~sre excellent (all gre~ter than or
equal to 82~, with the highest being 88%).
Analysis of bulk samples of the c8ra~ic materialq produced
in the pyrolysis of the various XH-catalyzed DHCD products shows
that a higher Si3N4/SiC ratio has been achieved ~Table 3~:
for the 1:1 coam~onolysis products-deriYed polymers, 86
Si3N4, 8~ SiC and 5~ C ~THF coa~onolysis) and 83~
Si3N~ SiC and 6~ C (E~20 ~o~mmonoly~is); for the 3:1
and 6 :1 coammonolysis products-dsriYed poly~ers: 779~ Si3N4,
18-199d SiC and 4-5~ C (Et20 cosmD~onolysis) and 743 Si3N4,
20~ SiC and 5-69~ C (THF cosmmonolysis).
~ owev~r, th~ KH-cata~yzed DHCD re~ctions w~th the 1:3
coammonolysis-derived polyner were 810w, producing soluble
products in poor yields. Pyrolysis ~f this material produced a
black ceramic.
ere are s~ tuations where one desir0s a cer2mic material
and/or preceramic polymer tbat co~tains differin~ amount~ of
silicon carbide ant silicon nitride. The present process can be
~sed to result in ~ preceramic polymer that will typically
produce a ceramic material that is enriched in silicon nitride
when compared to reactions in which the precursor dihalosilane
i~ ussd alone as the initial starting ~atesial.
For exa~ple, when Rl wzs CH3, X W8S Cl, and R was CH3,
CH2 CH or C2~5, the following results w~re obtaln~d.
As control experiments, ehe ~mono~ysis of CH3SiC13
alone was studied. Ammonolysis of this precursor in Et20 ga~e
-lS-
~:8~
46~ yiold of soluble ~olid jproduct, ~olecul~ lght 702
g/~ol, c~ra~lc yield (by TGA to 950C) 56~. A ~imilar
CH3SiC13/NH3 r~action ~n ~HF g~v~ ~olublQ ~olld product ln
824 yi~ld, mol~cul~r wslght 672 g/mol, c~ramic yi~ld (by TGA)
69~. By proton N~R (C~3Si/N~ int~graelon), the ~t20 product
~ay be fo D l~t~d 2~ [CH3Si(NH)1 3]x~ ~he T~F product ~3
[ 3 tNH)1,6]X. (This ls only n rou~h approxi~ation
because in~egrseion of the bro~d ~ si~n~ls is rath~r
inaccurate). The results of the coam~onolyses of CH3Si~C12
-16-
s
.TA~ 3
CH3SiHC12~
HSIC13 Molar
Ra5~o ~ Qduçt ~ ~ ELlL~ Si~
of a~monolysi~ 17.75 7.53 25.80
in Et20
6 of DHCD 20.05 6.73 25.82
ceramica 10.36 30.94 58.92
of ammonolysis
in Et20 16.19 7.31 27.04
3 of DHCD 17.61 6.46 25.85
ceramicb 9.35 30.79 59.99
. . . ~
1 of D~CD 14. la 6.12 27.60
c~r~icC 9.10 0.70 32.56 56.52
of ammonolysis
in THF 18.22 7.89 25.21
6 of DHCD 19.89 6.85 25.08
; cera~icd 11.72 29.71 59.03
of am~onolysis
~n THF 16.10 7.45 25.Sl
3 of DHCD 18.00 6.71 27.32
ceramice 11.21 29.77 59.09
1 of DHCD 1~.42 5.97
ceramicf 7.74 0.54 34.29 57.17
aCalc. 77% ~by weight~ Si3N4, 18~ S~C, 5~ C
bCalc. 77~ Si3N4, 19% SiC, 4% C
CCalc. 83~ Si3N4, 1;~ SlC, 5.7j C
dCalc. 74% Si3N4, 20~ SiC, 6~ C
eCalc. 74~ Si3N4, 20~ SiC, 5~ C
fCalc. 87~ Si3N4, 8~ SiC, 5.4~ C
-17-
?L~8'1~7S
and CH3SiC13 are giv~n in Tnbl~s 4 ~nd 5. In all CRS~g,
whethar the solvent wa-q Et20 ~r THF, oil3 w0r~ obtained ln
high yi~ld. rhesc w~re of low (300-500) ~olecular ~iBht ~nd
th~ir pyrolysis gsvs only low ceramic yi~ld~. The KH-cataly~ed
DHCD reaction of these coammonolysis products gAve whlte ~olid
products of higher (c~. two-to-threefold) ~olecular weight.
Based upon the lH NMR analycis~ the followlng formulatlons
of the products were generated:
cN3siHcl2/
CH3SiC13 Reaction
Molsr Ratio Solvent Formula
6 Et20 1CH3SiHNH]l.o[CH3Si(NH)1.5]0.26
IHF [CH3S~HNH]1 o[CH3Si(NH)2.1]0.27
3 Et20 [cH3si~NH]l.o[c~3si~NH)l~l]~29
THF [~3siHNH]l.o~cH3si(NH)l.l]~29
Et20 [c~3s~NH]l.olcH3si(~3H)l.s]o~63
THF [CH3S~HNH]l.olc~3si(NH)l~8]o.8o
Thes~ are only approxlmate con~qtitutions, but agreement ~f co~bustion
analysPs ~C, H, N) was fairly good for the formulaeions given. The
ceramic yields obtained on pyrolysis of these polymers were high:
78-82~ for the products generated by initial coam~onolysiq in THF. In
all cases, A black ceramic residue resulted when the pyrolys$s to
950G w~s carried out in a stream of argon. As expected, the carbon
content (in the for~ of SiC ~nd free C) was higher than that of the
CH3SiHC12/HSlC13-derlved ceramics (Table 6): 12-18% SiC, up to
9.~ carbon. Nonetheles~, hlgher Si3~4 contents than those
obtained when CH3SiHC12 is used alone ( 67%) were obtained.
DHCD products of polysilazanes ~ro~ ammonolysis in Et20:
75-76% Si3N4; 15-18~ SiC; 7 9~ C.
-18-
Ceramic
CH3S~HC12/CH3siC13 Yield
Co~monolys is
in Et20 6 oil 75 376 21
3 o~l ~0 ~73 40
oil ~1 526 44
1/3 w~x 89 627 --
- l/6whitc solid 65 642 --
DHCD R~action,
1% KHin l~F 6 ^qolid 97 12S0 82
~'
3 solid 100 795 78
solid 98 786 78
1/3 white solid95 850 58
1/6 white solid90 1012 56
-13-
. .
47S
~L~
Ceramic
CH3SiHCl~/CH3SiC13 Yleld
: Reaction ~ ~ Molar Ratio ~_ ~Product y~QLd~%) MW _ bv TGA.
6 oil 81 311 26
Coammonolysis
ln THF 3 oil 91 363 31
1 oil R9 434 44
; lJ3white solid 88
l/6white solid 98 -~
6solld 72 1171 86
DHCD R2action,
1% KH in THF 3solld 84 1173 83
1solid 100 838 82
1/3whlte solid 92 1180 76
1/6whits solld 9S 925 71
-20-
4~7S
~L~
C~3Si~C12/
CH3SiC13 An~ly.
Molar R~ti~ L~duct _ ~_ C.~ $i~
of am~onolysis
in Et20 20.248.02
6 of DHCD 21.857.09
ceramica 12.160.5l 30.44 57.23
~ . .
of ammonolysis
in Et20 20.017.90
3 of DHCD 21.677.26
ceramicb 13.040.72 31.05 55.30
. __ . ~ _ ._ .
of ammonolysis
ln ~t~O 19.66 7.49
l of DHCD 21.04 7.29 22.20
c~ramicC 11.36 0.61 31.90 56.35
. .. _ . . __ . ~
of ammonolysis
~ THF 20.26 8.06 23.79
6 of DHCD 21.85 7.02
c~ra~icd 12.37 0.60 29.35 53.94
of ammonolysis
in THF 20.13 7.93
3 of DHCD 22.05 7.03
cera~ice 12.36 0.63 29.57 56.77
-21-
4~75
of a~onolysi~
ir~ TllF 19 . 53 7 . 42
of DHCl) 22 . 35 7 . 24
cQr&micf 11.19 0 . 63 31. 01 56 . 36
aC~lcd. 76~ (by weight) Si3Nb" 16~ SiC, 7~ C
bCalcd. 78~ S13N4, 12~ SiC, g9~ C
CCalcd. 809~ Si3N4, 129~ SiC, 89~ C
dCalcd. 769~ S13N4, 15~ SiC, 99s C
eCalcd. 75~ Si3N4, 18~ SiC, 7'~ C
fCalcd. 79% Si3274, 14~ SiC, 7~ C
--22--
t~ 5
Chnnging the ~monomer~ r~tlo fro~ 6 ~o 3 to 1 do~ not v~ry the
compositions of the final cer~mic materlals very ~uch: th~ Si3N4
content vari~s by only 54, whila the SiC contene ~how~ a 6~ range ~nd
the carbon c~ntent i8 within 28 for ~11 the ~steriAls.
To produce a c~ra~ic m~erial containfng only S13N~, the white
sol~d polysila~ane derived from ~h~ DHCD of the oil obtalned by
ammonolys1s of 6:1 CH3SlHC12~CH3SiC13 in Et20 medlum wa~
pyrolyzed in a stre&m of ~mmonia ~to lOOOnC). ~ ~h~S~ ceramic
residue containing only 0.36% by weight C resulted.
Essentially the same reartions were carried out using
vinyltrichlorosilane in pl~ce of methyltrichlorosilane
~CH3SiHC12/CH2-CHSiC13 molar ratios of 6, 3 and 1; ammonolysis
in Et20 and THF medium; subsequent KH-catalyzed DHCD in THF: se8
Tables 7, 8, and 9). Control experiments lnvol~ing the amMonolysis of
CH2-CHSiC13 Alone, in Et20 and in THF medium, w~re also
performed. In both solvents, glassy white solids were obtained. The
yield of soluble products in Et20 was low (61~); in THF it was
quantitati~e. The molecular weights w~re relatively high (1165 and
1185, respectively) and the ceramic y~ elds obtained on pyrolysis to
950C wsre high (76% and 82~, respectively). This is a result, at
least in part, of a greater incorpor~tion of carbon. Analysis of the
ceramic obtained in the pyrolysis of the CH2-CHS~C13 ammonolysis
(in THF) product sho~ed a composition 71~ Si3N4, 29~ C.
The coammonolys~s of CH3S~HC12 and CH2-CHSiC13 in ~t20
" ~28~7S
CH3siHcl2/ Ceramic
C~2 CHSiC13 _ Yield
Co=onolys is
in Et20 6 oil 86 305 43
3 oil 87 333 53
oil 90 ~05 74
~ . . . _ _ __ . . _ ... -- . __ .... . _
DHCD React~ on,
1% XH in llHF 6 solid 99 880 83
3 solid 98 999 34
~olid 98 970 78
.
-2~-
~L2~1~75
~L~
~,~,~
C~i3SlHC12/ Ceramic
CH2oC}lSiC13 Yield
eact~o~_ ~loLar Ratio ~oduct~ ~d(~) ~ by TÇA~%
Coammonolysis
in l~lF 6 oil 89 350 47
3 oil 92 361 57
oil 94 536 74
DHCD Reaction,
1~ KH in l~lF 6 solid88 773 84
3 solid 100 716 78
solid 99 777 85
12~ 7
~L~
CH3siHcl2/
CH2-C~SiCl3 An~ly~is
~olar ~a~iQ Produc~ C~ ~L ~ % --
of = onoly~ls
in Et~0 22.80 7.86 23.91
6 of DHCD reaction 24.48 6.86 23.51
ceramica 17.06 28.33 54.62
.. . .... .. . ..
of smmonolysis
in Ee20 24.39 7.65 24.59
3 of DHCD reaction 26.21 6.89 23.31
ceramicb 17.21 28.43 54.91
of ammonolysi~
in Et20 26.83 7.08 24.73
1 of DNCD re~ction 27.66 6.48 25.14
; ceramicC 20.87 29.09 49.85
~Calcd. 71~ (by weight) S13N4, 17% SiC, 12~ C
Calcd. 71% Si3N4, 17% SiC, 12~ C
CCalcd. 73% Si3N4, 9~ SiC, 18~ C
dCalcd. 69~ Si3N4, 19~ SiC, 12~ C
eCalcd. 70~ Si3N4, 16~ SlC, 13~ C
~Calcd. 71% Si3N4, 11~ SiC, 18~ C
-26-
s
and in THF ~odiu~ ~av9 polysilaznn~ oil~ in hlgh yicld, nol~cular
weight3 300-600 g/mol. Pyrolysl~ of ths co~mmonoly~is product3 gave
hi8her cer~mlc yields, the higher the CH2~CHSlC13 oontent in the
chloro3ilane mixture. Appl~cation of the KH-cat~lyz~d DHCD raaction
to the ~mmonolysis products i~ all c~saq gave whlte solids of higher
molecul~r weight whose pyroly~l~ to 950C gava high (78-85~)
cerRmic yields. However, their S13N4 cont~nt wa~ lower and their
carbon content (as SiC + free C) w~s higher than observed in the
ceramics from the CH3SiHC12/HSiC13 and CH~SiHC12/
CH3S~C13 systems: For the CH3SiHC12/CH2 CHSiC13 ratio -
6 and 3 products: 69-71% Si3~4; 16-19~ SiC; 12-13~ C. For the
1:1 products: 71-73~ Si3N4; 9-11~ SiC; 18~ C.
A mixture of CH3SiHC12 and C2H5SiC13 (3:1 molar ratio)
was treated wieh ammonia in Et20 and in THF at 0C. In both
cases, sllazane oils, ~W 350-370, were obtained in hi~h yield.
Their cera~ic yields on pyrolysis to 950C were low (15~ ~nd 234,
respectively). Application of the DHCD reaction (1~ KH in THF) to
these oils ln both cases gave white sol-ds with increased ~ (972 and
860, respectively) and increased ceramic yield on pyrolysis to
950C (Bl~ and 78~, respectively). The pyrolysis product in each
case was a black foam when the pyrolysis gas stream was ar~on.
Analysis of the ceramic products ~a~e ~ C, N ~nd Si values from which
compositions of about 71-73~ Si3N4, 14-17~ SiC and 11-12~ C rould
be calculated. Th~, there i9 essentially no difference between
these results and the calculated composit~on of the ceramic product
of the corresponding 3:1 CH3SiHC12/CH2-CHSiC13 system (70-71%
Si3~4, 16-17~ Si~, 12-13~ C).
I~ the case of the present polymers, as is seen in Table 10, some
WerQ self-curing and on pyrolysis gave cera~ic ~ibers (those noted
lyesn). Others melted ~hen heated, so that the fibers ~ere destroyed
(those noted "non). Conversion of the meltable fiber to an infusible
ilber by a cure step prior to pyrolysis will enable one to melt spin
these materials into fibers.
-27-
~81~7S
~Q
CE~A~IC FI~R~ Q~m~l5_~ B_Ç~?Q~LI~L
Molar Am~onoly~ls FLbor on
CH3siHcl2/
CH2-SiCl3 6/1 Et20 xb Yes
n 3/l Et20 x No
1/l Et2 ~ No
n ~/1 THF x Yes
n 3/1 THF x No
n 1/1 THF x Yes
. _ . . . _ . .. . _
CH3SiHC12/
HSiCl3 6/1 Et20 x Yes
n 3/1 E~20 ~ Yes
1/1 Et20 x Yes
n 6/1 l~lF x ~0
3/1 THF x ~g
n 1/1 THF x Yes
.. _ , _ . .... _ .
CH3S iHG12/
CH3SiCl3 6~1 Et2~ x Yas
3/1 Æt2~ ~ No
1/1 Et~0 x No
. . ~
n ~/1 THF x Yes
3/1 - THF x ~o
n 1/1 THF x Yes
a Yes - Fibers re~alned after heating to 1000C under Ar.
No - Fibers did not remain after pyrolysis eo 1000OG.
b x means a bar was made and pyrolyzed to obtain a cera~ic bar.
-2~-
s
She ~curs~ step prior to pyroly~l~ cnn be ~ccompll~h~d when ~ith~r
R or Rl i~ alkenyl by curing the flbcr through hydrosilylstion. Thls
roaction can ba ~nduced by ultr~viol~t snd other high on~rgy radiation,
~s well as by ch~mical frcc radical ources and transitlon metsl
c~talyst~. $hasc compounds can resdily be ~el~cted by the per~on of
ordinary skill in the art and include H2PtC166}~20, p~roxlde
and a~o compounds, prefer~bly organic peroxides, such a-~ benzoyl
p~roxide, more preferably azo co~pounds such as azobisisobutyronitrile
and the like. Preferably, a rsdiatlon source is used.
W irradiaeion, irradiation with an slectron be~m or an X-ray
source, eec. will cure the alkenyl containing polymer~ Sub~ecting the
precera~ic fiber to W irradiation tRayonet Reactor) for 2 hours
results ln an infusible fiber that does not melt upon subsequent
pyrolysis under argon, producing ceramic fibers. By incorporating C-C
into the coa~monolysis product, this strategy can be broadly applied to
the present $nvention. The addition of a third co~pound containing an
unsaturated functionality to the ammonolysis ~ixture rasults ln a
mixture of oligomers. The particulRr amount to be ~dded to the
co~mmonolysis mixture will depend upon the desired use and compounds
being used.
~Fibers w~re prepared ln th~ following manner: In the dry box, a
;few drops of toluene was added to a poly~er sample and the resulting
~ix~ure ~tirred with a glass rod unt$1 a seicky residue resulted from
which fibers could be drawn. mes~ fibers (1/4" to 2" ln length) were
placed in a boat, taken out of the dry box and placed in a tube furnace
1ushed with Argon. The fibers were heated to 1000C ae
10C/~inute. The polymers listed in Table 10 were used ln preparing
f~bers.
~ he present polymers can be used as binders for SiC powder
processing.
Ceramic composite bars were prepared in the following manner:
In the dry box, a 100 ml, one-necked, round-bottomed flask was
charged with 0.6 g polymer and 2.4 g of commercial Fujima SiC powder.
-29-
She fla~k W~9 r~mov~d ~ro~ the dry box nnd ch~rgod wl~h 25 ml of
tnlu~n~. Th~ fln-~k wa~ piaced ln ~n ultrn~onic bneh for at least 15
minute~. The toluon~ was thcn re~ov~d on a rotary ~vaporator and the
re~idue thcn driad und~r vacuuu ~t 0.03 ~m Hg for ~t lcast 1/2 hour.
~he SiCJpolymer residue wa~ ground wlth & mortar snd pestle to produce
a fine powder. This powder was pres~d $n a 1.5" x 0.5" x 0.1~ die at
6000 lb~. for 5 ~inutes. The b~r was then iso~tatically pressed at
40,000 lbs. Finally, the bar ~as pyrolyzed under Ar in n tube furnace
to lO~O~C.
The polymers shown in Table 10 were used to form composite bars.
All bars r~tained eheir rectangulsr shape upon pyrolysis.
In a different embodiment, the polymeric silylamide which ~s the
intermediat~ formed from the DHCD reaction of [RlSiHX2] and
[R2SiX31 (wherein Rl, R2 and X are as defined above) can be
used to form another preceramic polymer. This polymeric silylamide is
the intermediate formed after the DHCD react5on and prior to treatment
with an electrophila, such ~s Ch3I. This inter~ediate species
(sometimes al~o referred to as a rreactlve 'living' polymer~,
silylnmide, poly(silylamide) or alkali mstal silylamide)~) can raact
with electrophiles other than CH3I. ~e have discovered that the
raaction of this silyamide with an organos~licon polymer containlng
Si-H repeat units ~referred to as an Si-H containing or~anosilicon
polymer) results in noval preceramic polymers.
The Si-~ containing or~anosilicon polymer ~s pref~rably a
polysilans compound of the for~ula [(RSiH)X(RSi)y~n~ ~where x + y
- 1, n is an Lnteger greater than 1, R is a lower alkyl group having
from 1 to about 6 carbon stoms, a substituted or unsubstltuted lower
nlkenyl group having from 2 to abou~ 6 ~arbon atoms, a substituted or
unsubstituted lower aryl group hnving from 6 to about 10 carbon atoms,
or a ~ri(lower)alkyl- or di(lowar)alkylsilyl group) (See U.S. Patent
Application Serial No. 756,353 filed July 18, 1985), a polycarbosilane
polymer containing repeat unit~ of the formula
[Rasi(~)-(c~2)q~,~-e-~
Ra
~~i~(CH2)q~ (II)
(where q is an integer 1 or greater, Ra is ~, a lower alkyl group
-30-
~,8 3L~75
havlng fro~ 1 to about 6 carbon atom~, n cyclo~lkyl group having from 3
to about 6 carbon Atoms, A substitutad or unsub~titut~d low~r alkanyl
group haviD~ fro~ 2 to about S carbon atoms or a qubstituted or
unsubstitut~d lowar aryl group h~ving fr~ 6 t4 abou~ 10 carbon atoms)
(Sec U.S. Pat~nt Application Sarial No. 781,934 filed S~ptember 30,
1985), or an organohydrogansiloxane polyw~r containlng r~peat units of
the for~ula [RbSi(H)O]n,i.~.,
~b
-~i-O- (III)
(where n is an lnteger 1 or greater, Rb is a lower alkyl ~roup havin~
from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to
about 6 carbon atoms, a substituted or unsubstituted lower slkenyl
group having from 2 to about 6 carbon atoms or a aubstltuted or
unsubstituted lower aryl group having from 6 to sbout 10 carbon atoms)
(Se~ U.S. Patent Application Serlal No. S49,390 filed April 8, 1986).
In accord with the present lnvention, treat~ent of, for example,
organopolysilanss ~ith the silyl~ide will provide higher moleculsr
weight preceramic materials and improve the ceramic yield.
~ e have now found that organopolysilanes ~uch as methylpolysilanes
([(CH3Si~)x(CH3Si)y]n) obtainsd in the above reactions, upon
treatment wieh catalytic quantlt~es of silyla~ides in accord ~ith the
present invention, yield preceramic poly~ers of hlghar molecular ~eight
which upon pyrolysis give slgniflcantly higher ceramic yi~lds. Such
polymers, when prepared as described herein, sr~ soluble in organi
solvents.
Polycarbosilane polymers that are used in the presant invention
preferably contain a multiplicity of repeat units of the fDrmula
[R~Sl(H)-(CH2)q~ (where q and Ra are as define~
abovR)(hereinafter polymers containing such repeat units are referred
to as "polycarbosilanesn). The reaction of thasc polycarbosilan~s ~ith
an alkali m~tal silylamide results in novcl preceramlc poly~rs.
Typically, the pyrDlysis of this na~ polymer gi~es a black cera~ic
47~j
~olid in a yiald thAt i~ gr~8tor ehRn th~t obtained on pyrolysi3 of the
parent polyc~rbosilan~.
The polyc~rbosllana poly~er ~hould contaL~ at l~ast 25 ~ola ~ of
rcpcat unit~ of th~ for~ula II, i.e. [RaSl~H~-~CH2)q], in additlon
to other repeat units, ~uch as [R82Si(CH2~q~ ~o.g. the Ya~ima
poly~ers). Prefersbly th~ polycarbosil~n~ polyuer contains nt least 35
mol~ ~ of repcat unlt~ of formul~ II. More praf~rably, the polymer
contains at least 50 mole 2 rop~at units of for~ula II.
The polymer may ~lso contain a mixture of repeat unies of ths above
described formula, e.g., both [RaSi(H)-(CH~)q] and
~R~Si(H)~(CH2)q~ (Ra' and q' sr~ d~fin~d the sa~e as Ra and
q, respectively, but Ra' may be different than Ra and q'may be
~ifferent than q). R~ is preferably a lower al~yl ~roup, ~ore
preferably Ra is CH3. Preferably q is ~ual to 1 - 3, ~ore
preferably it is equal to one.
The polycarbosilane.and silylamide ~r~ typically added in a ~eight
ratio of polycarbosilane: silyla~lde of about 10:1 or less. ~referably
this ratio is about S:l or le~s. More pr~f~rably the ra~io i~ ~bou~
3:1 or le~s. ~ost preferably the r~tio i~ about 1:1.
Additionally, the reaction of organohydrogensiloxane polymers
containing ~ plurality of repeat units of the for~ula [RbSi(H)O~n
(where n and Rb are as defined above) (herainafter poly~ers
containing such repeat units are refsrr~d to as ~polyslloxanesn), with
a poly(silylamide) also results in a no~el precera~lc polymer.
The pyrolysis of this new precera~ic poly~er under ~ strea~ of
ammonia typicslly results ln a high yield of a Yhite cer~mic material.
By choosing the correct stoichiometry one is readily able to obtaln a
ceramic material that is v~rtually only silicon oxynitride. This
process provides silicon oxynitrides at high yield and at low costs.
The pyrolysis of the preceramic polymer of the present invention under
an inert atmosphere such ~s nitrogen or argon typically r~sults in a
bl~ck ceramic solid in high yi~ld. This black ceramic mater~al
generally contalns SiC, S13~4 and SiO2 and can be used as a
binder or coating.
-32-
14'7~rj
The polysiloxane poly~r u~ad In the pr~nt inv~nti~n can be
r~dily obtainod by the hydrolysis o~ th~ appropri~t~ RbSlHC12
(wh~re Rb is as defin~d ~bove). Th~ hydroly31s ~ay be stcer~d to
givo a high yleld of cyclLc [RbSi~H)O]n oll,gomer or to produc~
hi8h~r molecular w~i8he l$near [RbSi(~)Ol polymers. They yield of
cyclic oligomers (n 4, 5, 6,...) ~ay be maxl~iz~d by using the m~thod
eaught by Seyferth, D., Prud'homme, C; and Wl~em~n, G.H-, Inor~. Che~h,
~: 2163-2167 (1983). Additionally, one can u3e com~erclally ~vailable
RbSi(H)O]n polymers.
The polysiloxane polymers useful in th~ present invention encompass
polymers having a wide rnn~e of ~RbSl(H)0] repeat units. The number
of repest units contained in the polymer will ~ary depending upon the
desired end product.
Preferably, the polysiloxane polymer shoul~ contain at least 25
mole % of repeat unlts of the for~ula III, i.e. IRbSi(H)O]n, in
addition to other repe~t units, for example, [R~R~ SiO],
~Rb Rb SiO], Rb ~nd Rb are dcflned the s~e ~s Rb;
and Rb, Rb , and Rb ay be the same A8 or d~fferent fro~ each
other. ~ore prefer~bly the polysiloxane polymer contain~ at least 35
mole ~ of rep~at units of for~ula III. Even more preferably, the
polymer contains at least 50 mole ~ repeat units of formula III. Most
preferably, the polymer contains at least 75~ mole repeat units of
formula III.
~ ith respect to the silylamid~ used, Rl is preferably a lower
alkyl group, ~ore preferably CH3, while R2 is preferably H or a
lower alkyl group, more preferably H or CH3. 2 is prsferably
chlorine, fluorine, bromine or lodine. The dihalosilane can be added
to the trihalosilane over a ~ide range, but preferably the mole ratio
of RlSiHX2:RSiX3 is about 20:1 to 1:20, more preferably it is
from about 8:1 to about 1:6, still more preferably about 8:1 to aboue
1:2, and even more preferably from about 6:1 to about 1:1.
This silylamide when pyrolyzed will eypically produce a cera~$c
material ~hat is richer in sillcon nitride than that obtained on
pyrolysis of the polysilazane DHCD pro~uct obtained from the
--33--
7~j
corre~pondine, dih~lo~lane ~lon~.
Th~ usc of the ~bo~s polyM~ri~ ~1lyl~mide in on~ embodim~nt of ths
presen~ inventlon up~radcs thc Si-H containing or~ano~llicon polymer,
for exampl~, the organopoly~ilan~s, the polycarbo~llanQs ~nd the
polysiloxanes to n~w polymers which giv~ a high ceramic ylsld on
pyrolysis. When this silyl~ide i~ react~d with an Si-H contnining
organosilicon polymer, tha reaction product after tr~atment with a
suitable electrophile such as an organic or a 5ilyl halide,
incorporates ~oth starting ~at~rials. When this reaction prod~ct is
pyrolyz~d, the csramic yield is signif~cantly greatcr than thst of the
"parent" organosilicon polymer. Additi3nally, the silicon
nitride/silicon carbide ratio of the resulting ~aterial can be varied
dependin~, upon the particular dihalosllane and trihalosilane, ratio of
dlhalosilane to trihslosilane and Si-H organosilicon poly~er used. The
ratios to use to obtaln a particular result can be determined
empiricAlly by the ~kllled artisan based upon the present disclosur~.
The w~ight ratio of Si-H containing polymer to poly~eric silylamide
can vary ~id~ly. For exa~ple, mole ratios of or~,anopolys~lsne:
polymeric sllylamide from about 4:1 to aboue 1:4, and pr2fsrably from
2.5:1 to 1:2 typically provlde useful r~sults. Ueight ratios of
polycarbosllane: polymeric silylam~de from about 10 to about 1; and
preferably fro~ 5 :1 to 1:1 typically provide useful results. ~eight
ratios of polysiloxane: polymeric silylamide of 1~ d 1:5 typioally
provided useful results. ~eight ratios of polysiloxane: poly~sric
silylamide from about 15 to abo~t 1 to about 1 to about 15, hould also
provide useful results. Preferably the weight ratio of polys~loxane:
polymeric silyla~ide ranges from about 5.1 to 1:5, and more pref~rably,
from 5:1 to 1:1. However, in all three cases other ratlos can be used
depend~ng on the particular starting materials and their pyrolysis
characteristics.
The organosilicon polymers thus formed by reaction of the
organosilicon polymer containing Si-H repeat units with the prsformed
silylamide ~ iDg intermediate" followed by treatment with sn
elactrophile, heneeforth ~ill be referred to as ~graft" polymers.
-34-
Poly~ n~s of typ~ (R3~H)n (iØ, ~h~ g~n~ral 08~ whora y - O,
x - 1) al~o r~act with th~ polymeri~ ~llylamido~ th~t ar~ tbe DHCD
resctlon product of ehe coa~onolysl~ of a dih~lo~llan~ ~nd
trihalo~ n~. Thus, a r~action of (C6H5SiH)~ ~lth the
~ilyla~id~ ~livlng intermediate" (1:1 ~olar r~tlo) ln THF at roo~
t~mperat~re ~iV~9 a new organo3ilicon polymer which 1~ an effective
ceramic precursor, giving ~ Si3N4/SlC/C cer~mic product ln hiBh
yi~ld upon pyrolysis eo lOOO-C.
Additionally, USQ of the resction product of or~anopolysil~nes or
polycarbosilanes with t~e polymeric ~llylamlde re3ults ~n a prod~ct
that is self-curing as the temperatuxe is raised in the production of
cer~Lc mseerial. Consequently, with these poly~ers lt is poss~ble to
avoid the formation of S102 which results when an oxidative cure step
i~ used. This again is an improvement over pyrolysis of the precursor
silane compound alone.
In ~his syste~, R or Ra is preferably a lower ~lkyl, ~ore
preferably, R or Ra i8 CH3. However, R or R~ need not b~ the
same and, as aforesaid, ~ixtures of Si-N containlng or~nosilicon
compounds and/or repeat unit~, e.g., [(RSiH)X(RSi)y~n and
[(~ Si~)x,~R Si)y,]n,> [RaSi~H)-(CH2)qJ and
[Ra Si(H~-(CH2)q~ and [(RSiH)X(RS~)y]n and
[RaSi(H)-(CH2)q] can be u3ed to obtain further flexibility in
tailorin~ the properties of the aforesaid product. Si~ilarly, m~xed
polymers of the type [(RS~H)a(RSi)b(RR Si)c]~ (~h~ e
~ nd R are a~ defined aboYe, and R ls defined a3 is R above snd
R may be the same or different than R) c~n be used as well.
Preferably, at least one of ehe grouping R, R', ~a, and Ra for
each mixture is CH3.
The polysiloxane polymer may also contain a ~ixture of repeat units
of the above described formula, ~ . g., both [RbSi(H)O] and [Rb
Si(H)O] ~Rb is defined th~ same as Rb but Rb' m~y be different
than Rb). Rb is preferably a lower alXyl group, ~ore preferably
Rb is CH3.
Further, these aforesaid ~ixtures of oo~pounds can b0 used to obtain
-35-
addltional fl~xibllity in tailoring the proporti~q of th~ sforesQid
produc t .
Mlxtur~s of polysllazanc~, for ~x~l~ whcr~ R2 19 H and R2 i3
CH3 also nu~y bc used.
A~ indicated abov~ hls inv~ntion also in/~luda4 th~ ca~e of
[ (RSiH)X(RSi)y]n~ wh~re x~ 0, with R ns defined sbov~. Thus,
[(RSiH)]n may be 2 linear or a m~xture of cyclic species, or a hybrid
of both types. For example, lPhSiHln (Ph i~ a phenyl group), cf,
Aitken, C. at al., ~ Qrganome~_h~ 2:Cll-C13 (1985), reacts in
the same way ~s ths above - described organopolysilanes ~o proYide ne~
organopolysilane/organopolysilazane hybrid poly~ers. These mixtures
will be particularly useful in ~tte~pts to avoid excess free silicon or
carbon. Similarly, aryl-substituted repeat units of zither
[RaSi~H)~(CH2)q] or [RbSi(H30], for example, where Ra or Rb
is a phenyl or substituted phenyl group, ~nd Ra and Rb can be a
lower aryl group is also lncluded.
The precera~ic product on~ obtains by using the~e silyl~mide~, aven
in only catalytic amounts, differ3 fro~ the starting organo~ilicon
compound. This difference in products apparently arises because both
Si-H and Si-Si bonds sre reactive towards nucleophilic rea~ents.
The "graft~ poly~er is for~ed by combining the already formed
polymeric silylamid~ with the Si-H containing organosilicon polymer,
for example, the or~anopoly~ilane in varylng proportions in an organic
solvant. Thereaftar, the mixture is seirred at room temperature for
~fficient ti~e for the two compound3 ~o react. In one e~botiment, the
polysiloxane, for oxample, [CH3Si(H30]n ol~gomers with a high
cyclic content, is added slowly to an organic solution such as THF
containing the prefor~ed silylamide. An im~etiate reaction with some
gas evoluei~n occurs. Thereafter, the ~ixture i~ stirred at room
te~perature for sufficient time for the two compounds to more
complctely reac~.
Any or~anic solvent in which both poly~er syseems are soluble
without reaceion can be used. Such organic solvents include, for
example, THF, diethyl e~her, glycol ethers, alkanes, arenes and
-36-
7~
combln~ions ther~of. Th~ tur~ may b~ h~at~d ~bov~ room
t~mper~tur~, and cnn b~ r~nu~d to ~peed up th~ compl~tion o~ the
r~actlon. A~tar rcfluxing, the ~ixtura 19 quenched with an
al~ctrophll~, E-Xl, to for~ the org~nosillcon ~graft~ poly~sr. The
el~ctrophile can b~ an alkyl b~lid~, sulfate, or sulfonate; a
halosilane; or the llke. Typic~lly, CH3I or a chlorosilane ls u3ed,
~lthough other ~qulvalent electrophlles well-~nown to those sk~ d ln
the art can also be used. ~ is preferably a lower Alkyl group or 8ilyl
group; Xl is preferably a halide, sulfate or sulfonate.
The organosilicon poly~er formed by tha present (~graft") process
with the organopolysilane is typically obtained ln yields greater than
85~ based on weight of the starting materials with a ~ariabls molecular
weight, typical values being in the 1600-2200 g/mol range. Thi5
preceramic orgsnosilicon poly~er can then by pyrolyzed ~nder ~nert
~tmosphere condltions (As used herein, nitrogen will be considered ~n
inert gas, argon is anoeher example~ to result in ~ cer~mic materi~l in
hlgh yield. Pyrolysis under nitrogen ~ave cer~mic prsducts in a yield
of 75-85~.
The orgaDosilicon preceramic polymers formed by the present
(ngraftn) process when polycarbosilane is uqed were produced in hlgh
yields (as hlgh as ss%). Pyrolysis of this precerAmic polymer gave
caramic products in a yield of 75-85~ (based on weight of the starting
materlals).
The resultant preceramic polymer when polysiloxane was u3ed were
produced in ~ood yialds, ~ypically better than 70%. The
polysiloxane-derived preceraQic organosil~con polymers can then by
pyrolyz~d under nitrogen or other inert atmosphere to result ~n
ceramic ~aterials in high yield. Typically, pyrolysls under nitrogen
gav~ black cer~ic products in a high y~eld (as h~gh as 88~). More
significantly, pyrolysis under ammonia will give a whi~e ceramic solid
in high yield. The white c~ra~ics contain little, if any, carbon.
What i9 referred to herein as sn "1~ ~iE~" polymer can be obtained
by carrying oue the DHCD reaction of the dihalosilane and trihalosilana
co~mmolysis product in solution in the presence of the Si-H containing
-37-
14t7~
organo~illcon poly~9r. In this mathod, the or~anopolysil~nt or
polycarhosilane ls added to ~n organic solv~9nt. Afterw4rd~, the
~ixture (generated by reacting in ~olut~on anhydrous a~onia with the
dihalosilan~ and trihalosilane) i9 add~d. The poly~iloxane i9 added to
tha coammonoly~is ~ixture which is in an organic solve9nt.
One then add~ to th~ solution a b~3ic cataly~t capable of
deprotonating tha hydrogen fro~ a nitrogan atom ad~acant to a silicon
&tom. See U.S. Patent No. 4,482,669. Th~9 re~ction ~ixture gradually
change~ color and hydrogen is svolv~d. The rasulting solution is then
stirred at roo~ ~emperatur~ for ~ufficient time for the silylamide
inte~mediates and the Si-H containing organosilicon poly~er to react.
It can b~ heated above room temperat~re, and can b~ heated at reflux to
speed the completion of the reaction. Afterwards, the reaction mixture
i~ allow~d to cool to room te~perature, if required, and quenched ~ith
an electrophile such as CH3I or a halosilane, such as a chloro3ilane,
to produce the organosilicon "~n situ" polymer. ~h~9 molecular weight
of the "i~ u9n polymer i9 variable. On pyrolysi~ this material
provide~ a high yield of a black ceramic material.
On pyrolysis the polycarbosilane-deri~ed material provides a yield
of a black c~ramic ~aterial, that ls typically greatar than that
obtained on pyrolysi3 of the polycsrbosilane ~lone.
On pyrolysls under nitrogen or ar~on the polysiloxane-derlved
material provide~9 a yiald of a black ceramic mat~rial9 thst is
typically greater than that obtained on pyrolysis o~ the p901ysiloxane
alone9. Pyroly~is under a~onia typically results ln qilicon oxynierides
in high yields.
The or~anosillcon poly~er formed by either of the abova ngraft" or
~ ethods usually is separated ~rom solution. The solvent i~
removed by using t~chniqu~s well known to a person of ordinary skill in
the art. One standard method i~ distillation, pr~ferably trap-to-trap
distillation. The polym~r, typically a whito powder that is solubla in
an organic solvent, is ther~by obtaI~ed. On~ ~ay also combin~
trap-to-trap distillation with centrlfuging, followed by trap-to-trap
dl~tillstion to separate the polymer from solution.
-38-
4~
The ~ln ~ prscar~lc polym~r difQr~ phy~icAlly ~ro~ the
~graft~ precsramlc polymer. Pla~or difference~ will be ob~erved in
thsir proton NMR spectra snd in the form of their thermogravimetrlc
analysis ~TGA) curves. Both types of polym~r8 Are useful ag preceramic
materials.
The u.4e of coammonolysl~-derivad, DHCD-catalyz~d ~ilylamide
described herein not only lmproves ths c~ramic yield of tha
organ4polysil~nes, but, more significantly, when thls silyla~ide is
reacted wieh organopolysilane of the formula [(~SiH)X(RSi)y]n in
the approprlats stoichiometry, the reaction product of
[(RSiH~x(RSi~y]n and the "livlng intermedi~te" cilyl~mide after
treatment with a suitable electrophile such as an organic or a sllyl
halide, incorporates both starting mAeerials. When this reaction
product is pyrolyzed, the excess silicon nor~ally obtained in the
pyrolysis of the or~anopolys~lane alone and the exc0ss carbon normally
obtained in the pyrolysls of the quenched poly~eric ~ilyla~ide alone
combine so that there i-~ no substantial excess of ~ieh~r element in the
ceramic product. Consequently, one can obta$n a cerA~ic material
preferably with less than about 1~ fre¢ sillco~ or free csrbon, more
preferably 18~s ehan about 0.5~ free carbon and le~s than 0.5~ free
sIlicon, and mo~t preferably with less than about 0.1% of free ~llicon
and less than ~bout 0.1% of free carbon, i.~ ceramic material
containing substantially no free carbon and nc free ~ilicon. The exact
combination of the two compounds necessary to r~sult in the d~sired
stoichiometry can readily be calculated by a pcr~4n of ordinary skill
in $he art on the basis of the re~ults of the ~nalyses of the ceramic
products obtained in the pyrolysis of ehe sepRrate polymers. Mols
ratios of organopolysilane: metal silyls~lde from about 4:1 to abou~
1:4, and preferably from 2.5:1 to 1:2 should provide useful results.
However, other ratios can be used depending on the part~cul~r star~ing
mater1al~ and ~heir pyrolysis characteristics.
The excess of fres carbon, which can be a proble~ with the starting
polycarbosilanes, can be dealt with by using a ternary system of: (1)
the polycarbosll3ne; (2) the polysilazane (as the polymeric silyla~ide,
-39-
4'7~
elth~r prcfor~d or K~n~ratud L~ ) and ~3) ~ poly~ no whos-
pyrolyqis alona givos a c~ra~ic produce which contalns 3n exces~ of
~ilicon. Ex~mpl~s of ~uch poly3ilsn~s ar~ org~nopoly~ n~ as
d~crlbed above, for ~xampl~, ehos~ which ~r~ produced by tha 30diu~
condans~tion of ~thyld~chloro~ilano. In th~s~ re~ctlon~ tho
organopoly~ nc i9 pra~erably a3 d3fin~d abova, i.c
[(RSiH)X(RSi)y]n~ More pr~f~rAbly R ls ~ lowcr ~llqrl group, mo~t
proferably ~ i9 CH3. U~lng ~n ~ppropriate ~l~tur~ of th~ thro~
poly~rs (which can be c21culated fro~ th~ resul~ of ~h~ analyse~ of
the csrn~lc product~ of the pyroly~l~ of ~ach individual polymer, ~.g.,
the CH3I- quench~d polymex in tha case of ths poly~erlc sllyla~id~),
one c~n obtain ~ ceramic product ~hlch contains a ~inf~al exces~ o~
~ither element, carbon or silicon. Such hybrid tern~ry precaramic
poly~ars are ~oluble in organlc solvents and, depanding on component
ratios usct, are of v~rlable ~olecular w~lghe. Their pyroly~i3 give~
black c~ra~ic product~ in high (generally > 80~) yiold.
I~ tho pr~c~r~lc poly~r which ro~ults fro~ a combinati~n of 8
poly-~ilo%~n~ poly~r (A) and ~ alk~ t~l (poly)~llyl~lda (B), th~
ratio of Si/0/~ of th~ r~ule~nl c~ramic ~etari~l can bc broadly varlsd
by ad~u~tlne the ~toichio~etry of th~ pr~c~ra~lc poly~r, i.~. the A:B
ratio. For ex~mplo, at on~ ~xere~o, th~ pyrolysl3 o ~
CH3I-quench~d ~ilyla~ld~ dcr~vo~ fro~ tho coam~onolys$~ of
CH3SlHC12 nnd HSiC13 and sub~u~nt DHCD rs~c~ion undor a NB3
at~o~ph~ro producod whit~ ~licon n~e~id~. By appropriate ~lact~on of
r~actsnt s~oichio~try it ~hould b~ po3~iblo eo obtain a coraDi~
prcduct that 1~ virt~ally puro ~llicon oxynltrid0.
For exa~pl~, it 3hould bo po~iblo to o~eain dlstinct cry~tall~ne
pha~ Si20~2 aft~r pyroly~i~ und~r a ~tr~a~ o~ oni~ fro~ a
prcceraDic p31ymQr one obtain3 by ~h~ proc~s~. In thi~
lnstanc~ th~ w~i~ht raelo o~ poly~lloxan~:alk~li Motal poly~sllyl~3ida)
i~ ~bout 1:1 and R and Rl aro CB3 and a2 1~ H or CH3. In th~
abov0-d~scrib~d sy~te~, dovlating from a 1:1 r~tio r~sults in a c~ra~ic
poly~er hæving 90~ Si3~4 wh~n you u~o mor~ poly(~llyamid0) or so~
SiO2 when you u~a ~oro poly~iloxano. It is ~i~pl~ to e~pirically
-40-
1475
dotor~ th~ appropri~ta w~lght ratio for ~ da~lr~d c0ra~ic product
with the w o of any of ~hs clai~d ~tartlng ~atorlal~.
Tho polysiloxane and qilyla~id~ ar~ typ~cally ~dded ln ~ weight
ra~io of polysilox~n~: sllyla~lds fro~ 15:1 to 1:15. Pr~ornb~y ehis
ratio i~ abo~t 5:1 to 1:5. Moro pra~orably tha ratlo 1~ about 3:1 ~o
1:3. Most pr~forably th~ rstio is about l:l.
Phy~ical bl~nd~ of Si-H containing organo~ilicon polymers, for
oxa~pl~ tha or~2nopoly~ilano, ehe polycarbo311~no poly~ oonta~ning
repe~ unit~ of [R~SS(H)-(CH2)q]~ for example, th~ Ya31~a
polycarbosilan~ or ths polysiloxane containing r~peat units of
~RbSl(H)O]n, with the ~quenched~ organo.~ilazane poly~er of U.S.
Patant Application Serial No. 899,471 can bo used sinc~ these will
rsact when thay ar~ heated togeth~r. When approximataly equal molar
qusnti~ies of the polymor~ wher2 R, Ra or R~ r CH3 ~ Rl -
CH3, ~ ~ H or C~3, are mixed and finQly ground tsg~thar and then
~ub~ectnd to pyrolysls to 1000C, cara~ic yialds ar~ obtaln~d which
aro ~pproxi~ataly th~ av~r~ga of tha cera~ic yloldJ when th-
organopolysilan~ ~nd tho organo~ zan~ poly~r~ ar- pysolyzad
~aparatsly, ~re significantly high~r than ehat wh~ch r~ult~ ~h~n tho
polycarbosllans 18 pyrolyzed 3~p~rat~1y and i~ ~till high~r than that
~hich resule~ wh~n tho polysiloxano i~ pyrolyzad ~oparately.
~ h~n polycarbo~ilano/or~ano~ilazan~ mix~re~ Aro h~at~d, l~ th~
3bs~nco of a solv~nt at 200C under nierog~n, whlt~ ~c~y ~ol~db ~r~
o~ta~n~d whlch sre insol~blo i~ nonpolar or~nic ~olYe~ hQn
or~anosilana/or~anosil~zano mixeur~ ara ho~o~, o~th~r ~ tho abs~nco
of a sol~nt at 100-C undor nitrog~n or ln ~ toluen~ ~olution ae
roflux, whita powd~r~ ars obtain~d which ar~ in~olublo in nonpolsr
organic solv~nc3.
TQrnarY bl~nd3 o~ the polyosrbosilan~, thc polysilaz~no and tho
(CH3S~U)~(C~3S~)yln polysilana b~havo si~ilasly.
Tho co~binot polymor~ obtalned by ~h~ ~gra~t,~ and
phy~ical blond ~othod3 can b~ convoreed to black c~ra~ic fib~r~.
Pyrolysis of pre~sad bar~ of the co~blnat polymar3 to lOOO~C provides
bl~c~ solld product. In oth~r 0xpcrl~nt~, o~llcon carbid~ powd4r is
~l~p~r~-d in ~ tolu~n~ ~olutlon cont~lnln6 25~ by ~lghe ~f eh~
o~blned orgsno~ilano/organo~ilaz~nQ poly~0r~. Th~ solvont 18
ovaporated ~nd ~he r0~idu-, ~ fins powd~r of ~illcon carbide ~ith
~ombined polym~r binder i~ pr~ss~d Into bar~ and pyrolyz~d At 1000-C.
A ceraslc bar is obt~lned showin~ ~ low w~lght loss And sll~htly
~hrunken 3iZ~.
Similarly, ~hen ~llicon c~sbide powder ~ dlsp~rsed In tolu~ne
~olu~lon~ of the co~b~ne~ polyc~r~osilane/organosilazane polymers, the
solvene evaporated and the residue, ~ fine pGwder of ~ilicon carbide
with co~bined polymer binder, is pr~ssed in~o bars and pyrolyzed at
1000C, a ceramic bar is obtAined ~howing a low weight 103s and
61ightly ~hrunken ~ize.
Pyrolysis of bsrs of the oomblned polysilox~ne-org~nosllaz~ne
polymers under ~mmonia results in a wh~te rectangular ~ody. Pyrolysis
~nder eithes pyrolysis condition r0~ults in oeramlc bar~ showlng low to
od2rat~ we~ght lo~s ar~d sl$ghtly ~hrunken D~Zel.
The l~vention will b~ furth~r lllustrat~d by the ~ples th~t
follow:
I . . ~Ç~
All r~ac~ions ~nd ~nlpulations were carri~d out under a dry
nitrogen ~no~phere u¢ing ~tand~rd Schlenk ~echniquen or ~ Vacuu~
At~o~pheres try 'box. All ~ol~rent~ ~ere distilled under n~trog~n:
di~thyl ~thor and tet~a~ydrofuran froDI sodiu~ b~nzoph~non~ l~etyl, ~nd
h~xane froJD lithiw12 aluminu~ hydrlde. Chloro~ ere obt~ined rcm
Petr~rch Syste~Ds, In~. or Sil~r Lsbs., Irlc. ~nd ~rQ distill~d from
~agnesium fillngs prior to u~e. Anhydrou~ ammonia (Matheson) was dried
by p~ssing through a KOH-f$11ed drying tub~. Hethyl iodide W85
di~tilled under nitrogen from P295. Potassiu~ hydrid~ ~Alf~ ~a~
obta~ned as ~ 40~ ~lurry in mineral oil which wa~ filtered, wash~d with
hexane and d~ied pr~or to use.
Proton NMR spectra were obtained on ~ithzr ~ Jeol ~X-9OQ ~90 MHz)
or a Bruker ~N-250 (250 ~Hz) using a CDC13 r~f~rsn~ (7.24 ppm
-~2-
... . . .
. . .
4~5
ehlft). Infr~rad ~p~cer~ ~r~ o~t~ln~d o~ P-r~in~ or ~odel 1439
l~fr~r~t ~p~ctrophoto~-tor,
~olocul~r ~clghe~ ~r~ d~ton~in~d by cryo~copy in bsnzone.
Thor~ogr~vi~ctric sn~lysi~ ~TGA) yi~ld~ ~or~ ~bt~ln~d u~lng ~
P~rkin-ElDler TGS~2 syse~m. S~plos ver~ ho~d fro~ 50C tD 950C
under ~n argon tmosph~r~ ~t 10C~ ln. Large-~c~l~ tubo furnace
pyrolyE~eh to produce gr~ qu~nt~ti~ of coraloics ~r~ p~rformed in a
Lindberg Mod~l 59344 tube furnace ~ith controllor. Sa~plos wero heuted
fro~ 200C to 1000C at 10C/~inue2 in an argon ~tmosphere.
~nalyses of all oils and poly~ers ~ere performed lby Scandinavian
~icsoan~lyticRl Lsbs, Herlev, DenE~rk. Cer~mic ~n~lyses were performed
by Galbraith L~bs, Xnoxville, Tennessee.
s~ 5len-
A typlcal r~action is describ~d. All other ~mmonolyses of the
~SiC13 ~lone or of mixtures of CH3S$HC12 ~ith RSlC13 (R ~ H,
CH3, CH2-CH) were carried out u~lng th~ ~ame gen~rsl proc~dure.
For ~ach ~H3S~HC12/RSiC13 ~olar r~tlo u3ad, ~psrat~ r~act~ons
w~re c~rrled o~t ~n ~t20 ~nd i~ THF ~diu~. Th~ yi~lds of ~olublo
protuct~ (solubl~ ~n the rosctio~ ~edium), th~ ~olecular ~ei~ht3, the
~rs~ic yl~lds (by TGA u~der ar~on3 obtain~d on ehelr pyroly~i~ and
their ~nalyses ~r~ given in the ~ppropri~ee T~bl~ 9~.
A 1000 ~1 three-necked, round-~ottomed ~las~ ~quipped w~th a Dry
Ice condens~r, an overhe~d ~echanical ~tirrer and a rubber septum ~s
1~-drl~d while a ~trcnm of dry D~trogen ~a~ passQd ehrou~h. Dry
di~thyl ~ther (600 ~ll V~8 ~ddsd and eh~n 33.6 8 (0.292 ~ol) of
CH3SiHC12 and 6.8 g ~0.05 ~ol) of HSiC13. Th~ solution was
cooled to 0C (~ce bath). ~he orlginal septum wa3 replaced with
another septum through ~hich a o~-foot gas inlet eube passed.
aa~aous ammoDia then wa~ bubbled into ehe ~olueion at B mod~rate rate
for 4.5 hours until ammonia ~as observcd condenslng on ehe -78C
condenser. Th~ a~monia inlet ~ube ~as replaced with a rubber septu~
~fter the addleion of ~m~onla had been stopped.
Tho r~ctlon ~lx~ur~ ~a~ l~llo~cd to ~ar~ to rooD t~p~tur~ and
stirr~d und~r nitrogon ov~rnlght. F~ltrseion ~in th~ dry box)
r~movot NM4Cl ~nd ~ny othar ln~olublo productD of tho r0-ction.
The ~olld3 ~ro w~shed with throa 50 ol portions o~ ~th~r.
~rap-to-trap distillatlon of th~ ~olY~nt (25C, 0.1 ~m ~8) fro~ th~
co~binffd ~th~r ph~s~ ft a cl~r, ~obllo oil ~l5.0 ~, 74% bssad on
th~ (CH3SiHNH) and [HSl(NH)l 33 component3). Th~ oll wa~
ch~racterl~ed by ~nnlysl~ (T~bl~ 3), by IR und H ~R
spectro~copy. Th~ ~ol~cular wel~ht wa~ ~ca3ur~d ~cryoscopy ~n
benzene) and a thermogravimetric tra~e wa3 obtained (50-950C,
10C pcr minu~
H NMR (250 ~Hz, in CDC13): ~ 0.17 (broad m, 2.6 H, CH3S~),
0.85 (broad m, 1.3, ~), 4.37 (broad 6, 0.25 H, SiN), 4.63 (bro~d s,
0.41 H, SiH) and 4.81 (broad s, 0.33 H, SiH).
IR (thln ~ilm, cm 1): 3380 (s), 2960~3), 2900(w), 2140-2120
(bro~d,~), 1545(w), 1405(m), 1255(s), 1200-1150 (bro~d, v~3, 980-750
(broad, vs).
~W: 390 ~m~l
TGA: 33~ by wsight c~r~ic r~Ridu~, black s~lid
. (Based on ~MR-derived for~ul~ 1~H3SIH~H]lHSl(NH)l 4]~ 17)
C~1cd f~r CHs.41N1.24Sil.17~ C~ 17- ;
Found: C, 17.75; H, 7.53; ~, 25.80.
III. ~
One such ~xperiment i~ de3cribed in ord~r to provide dbtai1s of
the prorodure u~ed. A11 reaction~ w~re c~rri~d out 1n IHF using 1
mol ~ of the KH catalyst. In all cases, the wh~ta solid poly~er
obtained after the CH3I quench ~as char~cterized by ~nalysis and IR
a~d lH NMR spectroscopy. The ~ol~cul~r w~ght wa3 m~asured by
cryoscopy in benzene and ~ thermal ana1ysis trace (TGA, 50-950
at 10C/minute, under argon) was ob~alned. The results of these
experiments are given in the Tables.
A 250 ml, three-necked, round-bottomed f1ask was equipped with a
-~4-
m~netlc ~tis-bar, a g~s inlot eubo and t~ rub~r septa ~nd ch~rg~d
wie~ KH (0.04 g, 1.0 m~ol). Th~ fla~k thon was connact~d to tha
nitroga~ lln~. Dry T~F (100 ~1) W~J addad by syrlng~ snd thon 6.355
8 (0-1 mol, b~d on CH3Si~N~ + [HSl(NH)l 5] unlt~) o tho
polysilazane oil (ob~ained by am~onDly~i~ of Y 1:1 ~olar ratio
~ixturu of CH3SiHC12 and HSiCl3 in dlathyl 4th~r~ ti~solvad ln
20 ~1 of T~F. Th~ latter solution wa~ add~d dropw~so ov~r a perlod
of 20 minutes. Gas cvolution (H2) wa~ ob~rv~d. Th~ r~sulting
clear solution wa~ ~tirred at roo~ t~psratur~ undar nitrogon for 1
hour. Sub~equently, m~thyl iodido (0.46 8, 3.2 ~ol) wa~ addod by
~yringe. An l~sdiate whlt~ preoipi~at~ of XI for~d. Th~ mixturo
waq qtirr~d for 30 minute~ at roo~ ta~perstur~ snd the~ the solY~nt
wa-c r~moved by trap-to-trap d~tlllation. To th~ r~idue was added
70 ml of benzen~ snd tha ~ixtur~ ~a~ centrifugcd to r~ovo
insolublo~. Ih~ 301ution phaso ~ rap-to-tr~p di~till~d (25C,
0.03 ~m Hg) to remova tho b~nzen~, loaving a ~h~eo organlc-solublo
~olid (',.41 8. 93~ yi~ld). (Ge,n~rally, in ~11 oth~r 3uch r~ctiona,
the raa~tion ~lxturo wa~ seirr~d for 1-18 ho~r3 ,se roo~ t~,~p~raturc
aft,3r th~ ~itial gas evolutlon was ob~,orvod. In th~ presene cas~,
~uch longar r~Action ti~,~s l~d eo ~or~atlo~ of ln~olubl~
lH ~MR (250 HHæ, in CDC133: ~ 0.17 (bro~d ~, 2.~ H,
CH3Si), 0.94 (broad, 1.2 H, NH~, 4.82 (brosd ~" 1.0 H, S~
IR(CC14, c3-l): 348,0 Sw), 3400(s), 2960(s), 2900(~ 120(s3,
1540(w), 1410(~), 1250(s), 1180-1130~bro~d,R), 1030~s),
970-8SO(broad,v~).
~: 1630 g~ ol
TGA (50-950Q, 10C p~r ~lnut~, und~r ar,g,on): 87~ c~ra~ic
yie,ld (black sol~d).
Q~l- Found: C, 14.10; N, 6.12; N, 27.60.
A 3 g sa~pls of this product wa3 pyrolyz~d ln a tubo urnac~ undcr
_~95_
4~
argon, l~Avi~g a r~id~e of 2.4 g (80~) ln th~ fon~ of ~ ohunk of
black solid.
~ l- Found: C, 9.10; H, 0.70; N, 32.56; Si, 56.52.
A~suming that all nltrogen is pre~ene a~ Si3N4, th~t ~h~ r~st
of the silicon ls pr~sent as SiC and tha~ thc rQ~aining carbon ls
presen~ ~3 free carbon, one can calcul~te fro~ ~hi~ ~nalysis ~he
composltion 1.0 Si3N4 ~ 0.46 SiC ~ 0.81 C or, by Yelght, 83
Si3N4, ll~ SiC snd 6~ C.
Pyrolysis of ehe whlte solid obtainQd from ~nother such
preparatlon (1:1 CH3SlHC12/HSlC13 a~monolysls in THF
followed by KH-cataly~ed DHC~ and CH3I quench; a 3.53 g sample)
ln ~ fus~d sil~ca bo~t in a tube furnace ~n a ~trea~ of ammonia
(25~-1000C within 3 hours) gave a whit~ powder resldue in
84~ by weight yield (100~ yi~ld based on the ~ilicon content of
the polysilaz~ne). Analysi~ indicated a carbon cont~nt of only
0.29~.
IV. Preparation o~ Organosilicon Compounds
1. p~,~,a~Qn o~,~(Ç~
tall operstions unde~ n~trog~n~ _
a. In ~F Mediw~.
A 500 ml, three-necked, round-botto~ed fl~sk equipped with a
stir-bar, a dropp~n~ funnel and n reflux eondenser was charged
with 50.5 g (2.20 g ato~) of Na m~tal. The flaqk ~a~ attach~d
to ~ Schlenk ~anifold, evacuated and ref~lled ~ith nitrogen
thr~e ti~es. THF (200 ~l~ was added snd the dropping funnel was
charged with 65 ml (0.625 ~ol~ of CH3Si~C12. ThQ s~lane was
added to th~ stirr~d ~a ~uspension during the coursa of 45 ~in.,
aft~r which time the reaction mixture was cloudy ~nd ~ligh~ly
warm. The ~ixture was stlrred for 16 hours at room te~perature
and 48 hours at reflux; i~ then was cooled to roo~ temperaeure.
Hexane ~60 ml~ was added. Th~ ~ixture was transferred by
cannula to a heavy-walled centrifuge bottle and cantri~uged.
-46-
~ 2~3~L47.~
The ~uporn~tant layar ~ tr~nsf~rr~d to ~ 1 lit~
round-bottomod flask (under nitrog~n). THF (50 ~ nd hexans
~30 ml) wera addod to tha rasidu~l ~ol.Ld and ~h~ ~sultln~
suspens~on wa~ centrifuged. The 3up~rnatan~ lAy~rs war~ combined
~nd 801vents wers r~ov2d by trsp-to-trap distillatLon ln vacuum
until ths residual liquid volum~ wa~ about 100 ~ 19 liquid
~a~ csnnulsted into a 250 nl ~ingle-necked flask and the
r~maining solvent WAS ramov~d in ~acuo t~ lenv~ 13.2 e (0.30 ~ol,
48% yield) of a white, glassy 8011~. OD b~ing h~ated ln a ~ealed
capillary (in YacUo) this solid soft~ned around 40-C and amsltsd"
between 130-140-C with gas evolution, leaving a ~hick gu~. There
was no further change up to 300~C excep~ fDr n gradual increase
in visc03ity. The product was poorly soluble ln hexane, only
somewhat soluble in benzene (precluding measurement of it~
cryoscopic molecular weight in thi~ solvent) and qulte soluble in
THF.
~NR (90 MHz, in CDC13): ~ 0.10-0.61 (~, SiCH3, 7.5H) and
3.55-3.90 (m, SiH, lH). Based on tho reasonable ~ssu~pti~n ehat
~very Si ~tom baaring a H substl~uent also bears a CH3
~ubstituent, the integrated CH3Sl and SlH intensiti~s lead to a
Constitution [~CH3siH)0.4(cH3si)o.6ln-
Calcd for CSiH3 4: C, 27.60; H, 7.87.
Found: C, 27.1B; H, 7.17.
IR (KBr, Nu~ol): 2170(sh), 2100(s, Si-H), 140B(m), 1260~m,
Si-CH3), 1249(s, Si-C~3), lG60(br), 1019(~), 931~s), 865(v~,
Si-CH3), 770(vs), ~85(~s), c~
TGA(25-lOOO-C, 10-C/min.): 60~ yield of a gray-black cer~m~c
~olld. A tube furnace pyrolysis of 3.20 g of this mater~l to
1500C ~ava 1.52 g (48~) of a gray ceramic powder.
An~ ~ . Found: C, 22.56; S~, 78.42; H,
0.01; ~, 0.009~. (SiC requires C, 29.94; Si, 70.06~; ac~ual
-47-
~1 2~4'7
co~position: SiC ~ 0.49 Si). X-ray powd~r diffraction (do~
A): 1.315(s) ~p-sic), 1.542(s) (~-sic~, 1.91(n~)
~s~ 8~ -sic), 2.52(~9) (,~ -sic), 3.13
si) .
A ~ass ~pectral analysi~ o~ th~ pyrolysis gas in ~nother
axperi~ent ~howed the following: no ~B5eoUa pr~duct3 wer~
obs~rved up ~n 385~C, then fragment ion~ corr2sponding w~ll with
th~ repcsted fragm~nta~ion of ~H3Si~3. At 445-C, C~3SiH3
was still observed and a pea~ at
m/z ~ 16 (CH4) began to grow in. By 580-C, when weigh~ loss
- was about over, only the ~ethane peak W8-~ ohservable.
b. In Hexane/lHF ~ed~u~
In a dry box, a 1 liter three-necked, round-bottomed flask equipped
with 8 stir-bar, a dropping iunnel and a reflux cond~n-~er ~as charged
with 75.0 g (3.26 ~ol) of sodium ~tsl. The flask was attached to a
Schlenk manifolt, ovacuat~d and flu3h~d ~ith nitro~en. THF ~70 ~1) and
hsxane (420 ~1) wera added and the dropping funnel wa~ charged wieh 150
~1 (1.44 ~ol) of ~thyldl~hlorosilane. ~ethyldichlorosilane was added
slowly into the ilask over ~ 3 hour period. The reactlon solution
turned purpl~ and by the end o~ the addition was at gentlc reflux. The
rcactlon mlxture was 3tirred at room temperatur~ for 2 hous~ and then
heated at r~lux for 16 hours. After it had been cooled to ro~m
tempera~ure, th~ reaction ~ix~ure (~xcept or the lar~e NaCl crystals)
~as ~ransferred via oannula into a h~avy-walled glass bottle. The
mixture was centr~fuged and the clesr, colorless supernatant layer
transferred by cannula into a 1 liter round-botto~ed flask equippQd
with a seir-bar. Hexane (200 ml~ and THF (20 ~1) were adtsd to the
remaining solids, the ~ixtur~ agaln was csntrifu~ed, and the
~up~rnatant liquid combined with ehs supernatant solution previously
separaeed. Solvent ~as re~oved by trap-~o-trap dis~illation until the
voluMe of th residue was about 100 ml, and the remaining liquid was
transf~rred by cannula into a weighed 250 ml round-bottomed flask.
--48--
:
4~t~
Ro~aining ~olven~ w~s romov~d by tr~p-to-tr~p di~till~t~on ~t
approxlm~t~ly 0.05 ~m Hg at roo~ ta~perature to givo 51.2 g ~31~, l.lS
mol) of a cloudy whlt~ oil.
H NMR (90 ~Hz, C~D6):~ 0.37 (brosd, SlC~3, 3.74N)
3.92 (broad, SiH, l ~).
NMR in~gration ~f the product gav~ a constitution of
[ (C~3s~)0.8(c~3si)o~2]n
IR (thin fil~, cm 1): 2967(s), 2900~), 2800~w), 2099(vs), 1410(s),
1385(w), 1249(s), 1055(br), 933(s) t 865(vs), 770(~s), 685(br), 650~sh),
585(w).
Molecular weight (cryoscopic in benzene): 600 g~mol.
~nal. (mater1al from another similar preparation). Calcd. for
CSiH3 76; C, 27.39; H, 8.55; Sl, 64.05. Found: C, 27.49; H, 8.98;
Si, 61.58%.
TGA (25-lOQ0C, 10C/min): 20~ yield of A gray-black ceramic solid.
Pyrolysis of ~ sample from another preparation in ~ tube furnace gavs a
~ray-black cera~ic solid in 36~ yield (by wei~ht).
~nal. ~of CÇ~ . Found: C, 22.93; ~1, 75.99~.
The pure liquid obtained by this procadure i3 ~ery alr-sensitive,
particularly ~hen its effecti~c surface area is high, ~8 ~hen in
contact wi~h a fritted funnel or & paper or cloth towel (in which c~ses
spontaneous inflammatlon may occur).
Other, ~imilar reactions have given 62-75% yields of
(CH3SiH)X(CH3Si)y~ Molecular weight det~rminaeions of several
preparations ranged from 520-740 g~mol. All products had very similar
lH NMR spectra, but with different SiCH3:SiH rat~os. Physical daea
of these products are liseed ln Table 11.
-49-
'75
~L~
P~YSICAL I~A FQR~a~.~;~L~
Sa~nple # Polymer M. W. a SiCH3: SlHb CeramicC x y Y~,e~
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 Q.86 0.14
aCryoscopic in benzene.
b lH NMR lntegration ratio.
CUnder nitrogen gas, 2S-1000C, lO-C~IDin (TGA)
--50--
4~
For tha pUrpO5e of ~impllfyin~ e~lcul~ion, ~ ~vora~ for~ula
w~ight vslua 44 wa~ assign~d for th~ u~it (~3S~H)~(CH3Si)y~
Therefore, ~n each of th~ following axperi~enta, the nu~bcr of mole~ of
th~ reaction unit (CH3~1H) wa~ calculae~d from the w~i~ht of th~
polymer us~d divided by 44.
The product formed in ehc T~F solution gi~es a 60% ceraMic yleld,
but le iq of li~ited solubility in org~nlc ~olvent~ ~nd it conversion
to ceramic fibers requires a curing step of photolysis/oxid~tion.
Preparatlon of the [~CH3SiH)X(CH3Si)y]n in ~ hexarle/THF
mixture of approximately 6 to 7:1 resulted in satisfactory yields of 8
soluble product. Howe~er, pyrolysis of this material resulted in vary-
low ceramic ylelds, rangin8 from 16 to 27~.
2. Characterization ~f the PolYcarbosilane
The polycarbosilane, a white solid, w8s purchased from Dow Corning
Corporation. The following dAta w~re collacted on ie:
H NMR (90 ~H~, C6D6): ~ 4.52 ~broad, Si~, lH)
0.26 (broad, SiCH3 ~d
SiCH2Si, 8.6H)
IR (KBr, Nu~ol, cm~l): 2104(s), 1253(s)~ 1014( , broad), 845(s,
broad~, 734(s).
Molecular U~lght (cryo~copic in benzene): 1210 g~mol
TGA ~25-1000C, 10C/~in): 58~ yield of a black c~ramic solid.
Tlj2 - 510C
3. Pre ~rat$on of SiL~
a. ~reParation of lcH~siLH)ol~(Iv-3l~
A 500 ml three-necked, round-bottomed flssk equipped with a
stir-bar, a reflux condanser, and a ~eruM cap was eharged with 90 ml
~0.87 mol) of CH3SiHC12 and 250 ml of CH2C12. To the solution
was addPd slowly (syring~ pump) 20 ml (1.11 mol) of H2O over a two
hour period. The reaction mixture was stirred at room temperature for
24 hours. Eight 100 ml portions of H2O were added to the reaction
-51-
'7~
Dixtur~. Th~ ~H2C12 l~y~r wa!i washed wlth two 100 81 portions of
H20 and drl~d ov~r H~S04. ~ solvent w~s r~moved by roenry
evaporation to give 44.5 g (85~ yield based on (CH3Sl~H)0~ unit) of 8
cle~r oll.
H ~MB (90 MHz, C6D6):~ 4.71, 4.69 ~broad, Si~, 1 H)
O.23, 0.21 (broad, SiÇ~3, 3 ~)
(neat, on 1): 2976(s~, 2918~w), 2162(5), 1410(w),
1260(s), 1030-1140 (broad,s~,
830-920 (broad,s), 769(s), 715(w).
Thls ls the procedure described by D. Seyfertb, C. Prud'hom~e and
G.H. Uise~an (Inor~. Che~ (1983) ~163) in ehe hydrolysis of
CH3SiHC12. A good yield of cyclic [CH3Sl(H)O]n oligomers ~as
reported, mostly n-4, 5 and 6, but some higher n (up to n-22) was also
obtained in lower yield. The ceramic yield of these oligomers is low
and will vary from 0 to 5 ~ dependin~ upon the pyrolysls conditions and
the particular ollgo~er used.
b .
IIL~ 2~~s ~
A 500 ~1 three-necked, round-bottomed flask equipp~d with a
stir-bar, a reflux condenser, and 8 serum cap ~as charged with 100 ml
(O 96 mol) of CH3SiHC12, 50 ml (0.41 ~ol) of (C~3)2SiC12, and
250 ~1 of CH2C12. To th~ solution eher~ ~as added 60 ml (3.33 mol)
of H20 (slo~ly by syringe pump~ over a 4 hour period. Reaotion
occurred im~ediately. The reactio~ ~ixture w~s ~tirr~d ~t roo~
temperature for 24 hours and then was washed with fifteen 200 ~1
portlons of H20 until the H20 washin~s ~ere neutral pH. The
~H2C12 layer was dried over MgSO4 and the solvent was removed by
rotary eYaporation ~o give 64.7 g (87~ yield by ~eight) of a clear oil.
H NM~ (90 MHz, C6D6):6 4.99 (broad, Si , 1 ~)
0.22, 0.16 (broad, SiCl3, 6H)
R (neat, c~ 2972(s), 2168(s), 1410(w), 1260~s),
1030-1120 (broad,s), B80(s), 836(s),
804(s), 769(s), 708(w)
-52-
,
C ~b9~5s~5~iLu~ 9~_5b~ lCH3S~(H)
P~-12~
(neat): 2982~), 2171~), 1413(w),
1262(s), 1030-1140 (~,brond),
860-905 (s,broad), 765(9), 718(w)
CD~-1
H ~B (C6D6):~ 0.25 (bro~d s, SiCH3, 3.4H), 5.04 (broad
s, SlH, lH)
Average Molecular Weigh~: 4500-5000 (vendor d~ta)
ceraT~R~ic Yield: (TGA, ~5-1000C., 10C./minute): 13~ (black solid)
V. Graft Reactions
A. Graft ~e~tion o~
Methyldichloro~ilane and viny~Lr~ 3~ ~o. ~H~ and
Polynethylhydridosilo7~ane Lp~_122LW~h P~um ~ drl~de in ~1~.
A 100 ml, three-necked, round-bottomed fl8s~ was equipped ~ith a
refl~x condenser with gas inlet tube on top, n ~tir-bar ~nd t~o septa
snd o~en-drl~d for 1 hour. (This will b~ tcrmed ehe asenndard r~action
~pparatusR.) Th~ apparatus wa~ taken lnto the dry box and char~ed with
potassium hydride (0.02 g, 0.50 mmol~ ~nd w~s then connected to a
nitrogen line, and charged with 50 ml of THF. ~he oil (1.64 g, 26.0
mmol) from the coammonolysis of CH3SiHC12 ~nd CH~-CHSiC13 (3:1
rat:Lo) in THF was added dropwise by syring~ 0~2r 15 ~in~tes. Gas
~volution wa~ ob~erv~d. Th~ reaction ~ixture ~as ~tirred for an
additional hour at room te~p~rat~re. By syringe,
polymethylhydridosiloxane (Petrarch syse~ms, Inc. PS 122) (1.59 g, 26.5
mmol) was added to the reaction ~lxture. After stirring 35 minutes,
methyl iodide ~0.46 g, 3.2 m~ol) ~as added nnd an im~ediate white
precipitate for~ed. The sol~ent ~as removed by trap-to-trap
distillatlon (25C, 0.03 m~ Hg) and the residue e~tracted with 40 ml
of hexane. The reaction mixture was c~ntrifuged and the supernatant
liquid cannulated into a 100 ml fl~sk. ~emoval of the hexane by
trap-to-trap distillation left a white solld (2.44 g, 75~).
-53~
lH NMR (CDC13, 250 MHz): S 0.17 (bro~d, 9.7 ~, SlC~3),
0.99 (broad, 3.0 H, NM), 4.38 (broad, 0.07 ~, SlH), 4.74 (broad, 0.93
H, SiH), 5.91 (bro~d, 2.1 H, SiCH-CH2).
IR (CC14, cm l): 3400(9), 3050(~), 3010~h), 2960(9), 2900(~h),
2140-2120 (bro~d, s), 1595(m~, 1405(~), 1270-1250 (broad, ~s),
1200-1020 (broad, vs~, 990-840 (broad, ~9).
MW (cryoscopy in b~nz~ne): 1340 gJm~l.
TGA (10CJmln, Ar, 50-950C): 36~ c~r~mic yield, black residue.
B. C~a~t Reacei~n of the Coammonolysis Produot o~_
thy~d~chloro$11ane and Vinvltrichlorosilane (3:1 Ra~i~lHF) and_
PolvmethylhYdridosilane with Potassium Hydride in ~HF~
The standard r~action apparatus was charged with potasslum hydrlde
(O.02 g, 0.50 ~mol) and 50 ml THF as previously described. The oil
(1.70 ~, 27.1 m~ol) fr~m the co~mmonolysis of CH3SiHC12 and
CH2-CHS$C13 (3:1 ratio) in THF ~as added dropwise over 15 minutes.
G~s evolution was observ~d. The reartion mixtuse w~s stirred an
additional ho~r at room temperature. Polymethyl~ydridosilane (1.24 g,
28.2 mmol) from the reaction o~ CH3SiHC1~ snd excess sodium in a
6:1 hexane~THF solvent mixture ~a3 added by syri~ge. Tha re~ction
~ixture became or~ng~ and then after 10 minutes turned yellow. The
reaction mixture was stlrred an additlonal 35 ~inutes at room
te~perature and then ~ethyl iodlde (0.46 g, 3.2 E~ol) was ~dded by
syringe. An i~mediate whlte precipitate formed ~nd the yellow color of
the re3ctlon mixtur~ ~as disch~rgad. The solvent was removed by
trap-to-~rap distillation and the residue extracted ~ith 40 ml hexane.
The r~action mlxture was centrifuged and th~ supernatant liquid
c~nnulated into a 100 ~1 flask. Removal of the hexane by trap-to-trap
distillation lef~ a whiee solid (2.74 g, 93~).
H N~ (CDC13, 250 MHz~: ~ 0.28 (broad, 3.1 H, SiCH3), 1.25
(broad, 0.55 ~, NH), 3.65 (broad, 0.21 H, SiH~, 4.38 (broad, 0.35 H,
SiH), 4.76 (broad, 0.44 H, SiH), 5.95 ~broad, 0.53 H, SiCH-CH2).
IR (CC14, cm 1): 3390(w), 3150(~), 3050(m), 2960(s), 2900(m),
-54-
~2J8~7S
2160-2140 (bro~d, v~), 1410(s), 1260(~), 1190-1140 (bro~t, 8), 1040-840
(bro~d, v~), 710 (v~), 590(w).
M~ (cryoscopy in bsn~n~): 1612 g/~ol.
TGA (lOGC/Din., Ar, 50-950C~: 864 c~ra~ic yi~ld, blAck solid
r~-cidue.
C. ~
Cornin~_~q~ 8) with Potassi~ Hydride in THF,
The apparatus was charged with potassium hydride ~0.02 g, 0.50
mmol) and ~0 ml of THF. The oil (l.S5 g, 26.0 m~ol) from the
coam~onolysis of CH3SiHC12 and CH2~CHSiC13 (3:1 ratio) in THF
was added dropwise by syringe over 15 minutes. Gas evolution was
observed. The reaction mixture was stlrred for ~n addit~onal hour at
roo~ temperature. Polycarbosilan~ (1.64 g, 28.0 m~ol, Do~ Corning
~9-6348) was ground to a fin~ powder with a mortar and pestle and
placed in a 25 ml, one-necked flasX. The flask w~s degasse~ and then 10
ml of THF was added. The resulting solution w~s cannulated into ehe
reaction mixture. After stirring for 35 minutes., methyl iodide ~0.46
g, 3 .2 mmol) was added and an immediate whlte precip~ate for~ed. The
solvent wa~ removed by trap-to-trap dist~llatlon (25C, 0.03 m~ Hg)
and the residue ~xtracted wlth 40 ml of hexans. The reaction mixture
was centri~uged and the supernaean~ liquid cannul~tedinto a 100 ml
i`lask. R~moval of the hexane by trap-to-trap distillation left a ~hlte
solid (3.04 g, 92~).
H NMR (CDC13, 250 MH2): ~ 0.16 (broad, 5.6 H, SiC~3), 0.95
~broad, 1.25 H, NH), 4.16 (bro~d, 0.3 H, SiH), 4.71 ~broad, 0.7 H,
SiH), S.91 (broad, 0.8 H, SiCH~CH2).
IR (CC14, cm~l): 3400(s), 3050(m), 3010(sh),. 2960(s), 2900(m),
2120-2100 (bro~d, s), 1600(w), 1410(s), 1360(m), 1270-1250 (b~oad, vs),
1190-1130 (broad, vs), 1050-84a (broad, vs).
~W (cryoscopy in benzene): 862 g/mol.
~ ~L~3L4~7~
TGA (10C/~in., Ar, 50~g50C): 85~ c~r~mlc ~l~ld, black so11d
residua .
D.
A three-neckad ro~nd-b~ttomed flask waq equipp~d with a ga~ inle~
tube, ~ stir-bar and two septa, o~en-dried for 1 hour and then w~
charged wieh pot~ssium hydride (0.02 g, 0.50 ~ol). The app~ratus was
then connected to a nitrogen line and 50 ml of THF was ~dded. The oil
(1.64 g, 0.029 mol) from the coammonolysis of CR3SiHCl? and
RSiC13 ~3:1 ratio) ln THF, was ~dded over S minutes. Gas evolution
was observed. The reactlon mixeure was stirred for an additional 45
minutes at room temperature. ~y syringe, polymethylhydridosiloxane
(1.58 g, 0.026 mol., Petrarch Systems, Inc., PS 122) was added to the
reaction ~ixture. After stirring 30 m~nutes, ~ethyl lod~de tO.46 g,
3.2 mmol) WBS added and an im~edlatP white precipitate for~ed. The
~olvent was removed by trap-to-trap distillation (25C, 0.1 ~m ~8)
~nd the ~esidue extracted with 40 ml ~f hexane. The reaction mlxture
was centrifuged and the supernatan~ liquid cannulst~d lnto a 100 ml
flask. Re~oval of the h2xane by trap-to-trAp dlstillation left ~ white
solid (2.30 8, 71%).
H NMR (CDC13, 250 HHz): ~ 0.10 (broad, 4.5 H, SiCH3), 0.93
(broad, 2.0 H, NH), 4.84 (bro~d, 1.0 H, SiH).
IR (CCl4, cm~l): 3490(w), 3400(s), 2960(s), 2900(w?, 2870(3h),
2820(w), 2130(s), 1580(w), 1425(m), 1265 ~broad, 5), 1200-1020 (broad,
vs), 980-850 (broad, V5).
MW (cryoscopy in ben~ene); 1855 g~mol
TGA (10C/min, Ar, 50-950C): 88% cera~ic yield, black s~lid
residue.
-56-
~2~1~75
E. ~ ~ L~ I--WL ~ _
~.
The apparatus w~s chnrged wlth RH (0.02 8, 0.50 ~ol) and 50 ~1 of
THF. Tha oil (1.77 g, 0.031 mol) from the co~Q~nolysis of
C~3SiHC12 and HSiC13 (3:1 ratio) in THF wa3 added over 5
minutes. Gas evolution w~ observed. Th~ r~act~on m~xture was stirrQd
~n addition~l 45 minutes at room ~empersture. Polymethylhydridosilane
~1.30 g, 0.030 mol) from the reaction of C~3SiHC12 ~nd excess
sodium in 6:1 hexane/THF was added. The reaction mixture bec~e orange
and then after 10 minutes t~rnsd yellow. The rea~tion mixture was
stirred an additional 30 minutes at room te~perature and then methyl
iodide (0.46 g, 3.2 m~ol) was added. An 1~m2diate white precipitate
for~ed and the yellow color of the m~xture was discharged. The solvent
was removed by trsp-to-tr~p distill&tion and the residue extracted wtin
40 ml of hexane. The resction m~xture wa~ centri~uged an~ the
supernatant liquid cannulated into ~ 100 ~1 flas~. Remov~l of the
h~xane by ~rap-to-trap distillation lef~ a whit~ solid (2.70 g, 88%).
1~ NMR (CDC13, 250 MHz): ~ 0.30 ~broad, 2.6 H, SiCH3), 1.23
(broad, 0.58 H, NH), 3.65 (broad, 0.19 H, SiH3, 4.4 (broad, 0.28 H,
SlH), 4.8 (broad, 0.53 H, SlH).
IR (CC14, cm~l: 3S70 (broad, w), 3490 (m), 3150 (s), 3060 ~s),
2960(s), 2900(w), 2280(s~, 2150 (broad, vs), 1815(s), 1570~w), 1415(s),
1265(s), 1190 (broad, w), 1050-1020 (broad, vs), 980-850 (broad, ~s),
700(w).
NW (cryoscopy in benzene): 2200 ~/mol
TGA (10C~min., Ar, 50-950C): 75~ ceramic yield, black solid
residue.
-57-
~%~ 7~rj
F.
X~-6~48L ~ ,5~LL~ L ~IY~
The apparatu~ was char~d v$th KH ~0.02 g, 0.50 ~ol) ~nd 50 ~1 of
THF. The oil (1.61 g, 0.028 ~ol) from tha coaDmonoly~is of
CH3SiHC12 snd HSlCl3 (3:1 ratio) in ~HF was ~dded ov~r 5
minutes. Gas evolution was obs~rved. ~he re~ction mixture was stirr~d
an additional 30 minutes at roo~ temperature. Polycarbosilane (1.45 g,
0.025 mol, Dow Corning X9-6348) w~s gro~nd to ~ fine powder and placed
in 8 25 ml one-necked flask. The flask was degassed ~nd then 10 ml of
THF was added. This solution was then cannulated into the re~ction
m~xture. After stirring for 30 minutes, methyl iodide (0.46 g, 3.2
m~ol) was added and an im~edlate white pr~cipitate ~ormed. Th~ solvent
W8S removed by trap-to-trap dlstillation (25C, 0.1 m~ Hg) and the
residue e~tracted with 40 ml of h~xane. The reaction mixture ~a~
centrifuged ~nd the supernatant llquld cannulated into a 100 ml flask.
Removal of the hexane by trap-eo-trap di~t~llatlon lcft a white 301id
(2.97 g, 95~).
H NMR (CDC13, 250 MH~ 0.16 (broad, 5.0 H, SlCH3), 0.95
(broad, 0.8 H, NH), 1.24 ~0.7 ~, NH), 4.4 (broad, 0.3 H, SiH), 4.8
(broad, 0.7 H, Si~).
IR (CC14, c~-l): 3490(w), 3400(s), 2960(s), 2900(~), 2875(sh),
2120 (broad, s), 1460(w), 1415(D)~ 1365(~), 1260(s), 1175 (broad, vs),
1030 (broad, ~), 1080-850 (broad, vs).
M~ (cryoscopy in benzen~): 845 g/mol
TCA (10C/min., Ar, 50-950~C): 76~ cer~mic y~eld, black solid
residue.
i:
-58-
~L~2
~Q
C~rsmic
Yield
Rça~tlQn
3:1 CH3SiHG1
VlSiC13 (THF)
with KH/PS 122 solid 75 1340 86
3:1 CH3SiHC12/
ViSiC13 ~THF) solid 92 862 85
with KH/D.C. Polycarbosilane
3:1 CH3SiHC12/
ViSLC13 (THF) solid 93 1612 86
wi~h RH/(CH3siH)0~78
(CH3SI)~.22
3:1 ~H3SlHC12/
HSiC13 (T~F)
with KH/PS 122 301id 71 1855 88
3:1 CH3SiHC12/
HSiC13 (THF) solid 95 845 76
with KH/~.C. Polycarbosilane
3:1 C~3S~HCl2/
HSiC13 (THF) ~olid 88 2200 75
with KH/(CH3SLH)~),
CH3Si)o 22
: Vi ~ vinyl
~ -59-
'7~
VI. ~In-Situ Procedure~
A. ~ ~ ~ Ç13
Lf~2~f~y~
In ~ dry box, a 250 ml round-bottom~d flask equipp~d with a
~eir-bsr, reflux condenser and a ~erum csp i8 charged with 0.10 g of KH
(O.0025 ~ol). ~HF (50 ml) is added to suspend the KH. A separate 250
ml Schlenk flask is charged ~th 2.0 8 f a CH3SLHC12/HSiC13
co~mmonolysis mixture that is prepared as described in section II.
This mixture is prepared by = onolysis of CH3SiHC12 and HSiC13
in ether solution, and then combined with 2.2 g of
[(CH3SlH)X(CH3Si)y]n (0.05 mol, x - 0.74, y - 0.26), and 100
ml of THF. The mixed polymer solution ls transferred by cannula into
the KH suspension. The reaction mixture gradually changes color to
light orange and hydrogen gas is slowly e~olved. The resulting
solution is st~rred at room temperature for 14 hours and i5 then heated
at reflux for 1 hour. The light orange color of the solution
persists. The reaction mixture is allowed to cool to room te~perature
and 0.5 ~1 (7.9 ~ol) of CH3I is added to for~ a whits precipitate.
Th~ solvent ls removed by trap-to-tr~p distill~tion. The product is
extracted with 200 ml of hexane and the insoluble residue is removed by
centrifugation.
The clear, colorless supern~tant layer is tr~nsferred ~la cannula
into a weighed 250 ml round-bottomed flssk The hexane is removsd by
trap-to-~rap d~stillatlon lea~ing 3.8 g (91~ by weight~ of ~ white
powder. The latt~r is soluble in THF, benzene, and he~ane.
2. Vs~ a co ~m~n~lysis mixture of ~H3SiHCl~ SiCl3 ~repared in
Acoording to the procedurP de~cribed above, the reaction between
0.1 g of R~ (0.0025 mol), 2.0 g of the coaGmonolysis product of
CH3SiHC12/HSiC13 (prepar~d in THF solution), ~nd 2.2 g o~
-60-
t8~4'75
[(CH35iH)X~CH3$i)y]n (x ~ 0.74, y - 0.26) 1~ c~rrled out
under nltrogen. The r~ulting rsaceiDn mixture al~o graduslly change~
color ~o llght orange wlth ~low ~volution of hydroge~ ga~. Th~
~olution is stirr~d ~e room t~mp~rature for 14 hours ~nd th~n 0.5 ~1
(7.9 mmol) of CH3I is added. ~ork-up &~ described in th~ pre~ious
experiment leaves a ~hlt~, solubl~ ~olld.
B. 8~~ctiQna o A Ml~lr* ~ oa~D~ly~ æ~tur9 ~nd
po~,ycar~Qsllane wlth-~ Catal~t~
1. Uslng a Coammonol~is Hixture o~ SiHCl~ 3_
Pre~E~d from ~iethvl Ether.
c. PolYcarbosilane/Coammonolysis ~i~ture_in l;l wei~ht
~i~ '
In a dry box, a 250 ml round-bottomed flask equipped with a
stir-bar, reflux cond~nser and a serum cap is charged with O.lS g of ~H
(3.75 mmol). T~F (50 ml) is added to suspend the ~H. A separate 250
ml Schlenk flask is charged wtlh 5.0 g of the coa~onolysis product of
CH3SiHC12 and HSiC13 prepared in ~ther solution, Qnd 5.0 g of
polycarbosilane, and 150 ml of THF. The ~i~ed polymer solution 1s
transferred by cannula into the KH s~spension i~ THF. Ihe reaction
~ixture grsdually turns clear and hydrogen gas slowly evol~es. The
resulting solution is stirred at room temperature for ~ hours snd is
then heat~d at refl~x ~or 24 hours. The reaction ~ixture is allowed
to cool to room temperature and 0.5 ~l (7.9 ~ol) of CH3I i~ added
and the -mixtu~e i5 heated for several hours. The sol~ent is remo~ed by
trap-to-trap distillation. The product i3 extracted with 200 ~1 of
hexane and the insoluble residue is re~oved by centrifugation. The
clear, colorless supernstant layer is tran~ferred v~a a cannuls into a
weighed 250 ml round-bottomed flask. The hexane is removed by
trap-to-trap distillation leaving a white powder. The white powder is
soluble in THF, benzene, and hexane.
C. ~eactions of a ~ixture of a Coammonolysis Mixtu~e and cyclic
Ql~ withlgi_~QtalYg5
-61-
~ 2~
In a dry box, a 250 ml round-botto~0d ~lask ~quipped with 3
stir-bar, reflux condens~r, ~d ~ saru~ c~p i~ char~od with 0.1 g of XH
(2.50 mmol). THF (100 ~ dded to susp~nd the KH. A separAte 250
ml flask is ch~rsed with 4.0 g of the product, prepared by
co~mmonolysi3 of CH3SiHC12 and ~SiC13 in THF ~olution, and 3.6 g
of [CH3Si(H)O~n, and 50 ml o THF. ~his soluelon is transferred by
cannula into the KH suspens~on in THF. Th~ reaction mixture ~radually
turns clear ~nd hydrogen gas is slowly evolved. Tbe resulting solution
~s stirred ~t room temperature for 4 hours and then 0.5 ml (7.9 mmol)
of CH3I is added. The solvent is removed by trap-to-trap
distillation. The residual solid is treated with 80 ml of hex~ne and
the insoluble residue is removed by centrifugation. The clear,
colorless supernatane layer i~ transferred via rannula into a weighed
100 ml round-bottomed flas~. The h~xane is removed by trap-to-trap
distillat~on leaving of a white powder. The latter is soluble in THF,
benzene, and hexane.
This invention has been de~cribed in detail with reference to the
preferred embodiments thereof. However, it ~ill be appreciated that
those skilled in the art, upon consideration of this disclosure, may
make modificatlons and i~provements witbln the spirit and scope of the
invention.
-62-
