High performance siloxane-containing polymers

Article abstract of DOI:10.1080/15421400490478920

Catalytic cross-dehydrocoupling polymerization of silane and water, and deaminative polymerisation between silanol and aminosilane are used to synthesize a variety of silicon-containing polymers with controlled structure. n-Hexylamine-2-ethylhexoate was used to catalyze silanol condensation. Among transition metal derivatives investigated, Pd₂(dba)_s is the most active catalyst for the dehydrocoupling polymerisation, and deaminative polymerisation proceeded smoothly by heating. Optically active siloxane materials of branched structure were obtained from (S,S)-1,3-dimethyl-1,3- diphenyldisiloxanediol and (S,S)-1,5-di(1-naphthyl}-1,5-diphenyl-1,5-divinyl-3- methyltrisiloxane (>99% ee) as optically active building blocks.

Full text of DOI:10.1080/15421400490478920

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High Performance Siloxane-
Containing Polymers
a
Yusuke Kawakami∗ , Ichiro Imae a , Motoi Oishi a ,
Makoto Seino a & Yang Liu a
a Graduate School of Materials Science, Japan
Advanced Institute of Science Technology Asahidai
1-1, Tatsunokuchi, Ishikawa, 923–1292, Japan
Version of record first published: 18 Oct 2010.
To cite this article: Yusuke Kawakami∗ , Ichiro Imae , Motoi Oishi , Makoto Seino &
Yang Liu (2004): High Performance Siloxane-Containing Polymers, Molecular Crystals
and Liquid Crystals, 415:1, 75-92
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Mol. Cryst. Liq. Cryst., Vol. 415, pp. 75–92, 2004
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400490478920
HIGH PERFORMANCE SILOXANE-CONTAINING
POLYMERS
Yusuke Kawakamiꢀ, Ichiro Imae, Motoi Oishi, Makoto Seino,
and Yang Liu
Graduate School of Materials Science, Japan Advanced Institute of
Science and Technology, Asahidai 1-1, Tatsunokuchi,
Ishikawa 923-1292, Japan
Catalytic cross-dehydrocoupling polymerization of silane and water, and
deaminative polymerisation between silanol and aminosilane are used to
synthesize a variety of silicon-containing polymers with controlled structure.
n-Hexylamine-2-ethylhexoate was used to catalyze silanol condensation. Among
transition metal derivatives investigated, Pd2(dba)3 is the most active catalyst
for the dehydrocoupling polymerisation, and deaminative polymerisation pro-
ceeded smoothly by heating. Optically active siloxane materials of branched
structure were obtained from (S,S)-1,3-dimethyl-1,3-diphenyldisiloxanediol
and (S,S)-1,5-di(1-naphthyl)-1,5-diphenyl-1,5-divinyl-3-methyltrisiloxane
(>99% ee) as optically active building blocks.
INTRODUCTION
Modern advanced technologies have continuous demands on the develop-
ment of high temperature heat resistant or flame retardant materials. As
elastomers for electronic application, thermal stability up to several hundred
degree is required simultaneously maintaining flexibility to temperatures
much lower than ambience. In conventional technologies, halogen, nitrogen,
or phosphorous containing polymers are widely used as heat resistant or fire
retardant polymer, such as fluorocarbon polymers [1], polyimide [2], poly-
phosphazenes [3]. The drawback of these materials in application is possible
emission of toxic and corrosive gasses during combustion.
This work was carried out partly in Nanotechnology Glass Project as part of Nanotechnol-
ogy Materials Program supported by New Energy and Industrial Technology Development
Organization (NEDO).
Corresponding author. Tel.: þ 81-761-51-1630, Fax: þ 81-761-51-1635, E-mail: kawakami@
jaist.ac.jp
75

76
Y. Kawakami et al.
Polysiloxane is a kind of another good candidate for such functional
materials because of flexible and heat resistant Si-O-Si backbone, which
is also the origin of good dielectric and surface properties [4,5], and
silarylene-siloxane polymers, derivatives of polysiloxanes by partially
replacing -O- by arylene groups, show better mechanical property than
polysiloxane [6,7]. Corriu [8] elucidated that the main course of degradation
of these polymers is the intermolecular followed by intramolecular
exchanges of Si–O bonds leading to depolymerization.
Silphenylene-siloxane polymers can be synthesized from 1,4-bis(hydroxy-
dimethylsilyl)benzene (BHSB) and difunctional silane or siloxane. Variety
of functional substituents, such as vinyl, phenyl, hydrido, and flouroalkyl,
can be introduced into the polymer structure. Among them, vinyl group
was found superior to others for enhancing the thermal stability [9,10].
Merker reported polycondensation of BHSB to give poly[(oxydimethyl-
silylene)(1,4-phenylene)(dimethylsilylene)] [11], commonly called as
poly(tetramethyl-p-silphenylenesiloxane) (PTMPS). This PTMPS con-
tains the maximum number of rigid phenylene groups, and should be more
reluctant to siloxane rearrangement and highly thermally stable. Mean-
while, we reported a clean method to obtain PTMPS by catalytic cross-
dehydrocoupling polymerization of 1,4-bis(dimethylsilyl)benzene with
water under neutral condition [12]. However, PTMPS is not good as high
temperature elastomer because it is crystalline, and proper chemical modi-
fication of the structure should be made to gain low temperature elasticity.
We recently reported a kind of poly(silphenylenesiloxane)s containing sili-
con hydride and vinyl side groups, which have been proved to be promising
candidates for high temperature elastomers [13]. Vinyl side functions,
besides high temperature vulcanizable nature, can also be chemically cured
or modified by various reactions such as hydrosilylation to give the polymer
new functionality or a 3-D network structure. The cross-linking density
may also be controlled over a broad range depending on the ratio of the
cross-linker to vinyl groups.
Poly(silsesquioxane), having the empirical formula RSiO1.5 (R ¼ Ph, Me,
H etc.), is another kind of interesting silicone polymer. It also shows excel-
lent properties, such as high thermal stability, low dielectric constant, oxi-
dative resistance [14], and establishment of reliable synthetic method is
still required. Considerable attention is also given to highly branched three
dimensional macromolecules such as dendrimers and hyperbranched poly-
mers due to the wide applicability to novel macromolecular architecture
and functional polymers [15].
Meanwhile, much attention has been also paid in recent years to the
fabrication of chiral polymeric materials. However, many materials with
chirality induced by asymmetric silicon atoms in the main chain have not
been reported yet, although chirality is introduced to the side chain or

High Performance Siloxane-Containing Polymers
77
the main chain [16]. We have prepared several stereoregular and optically
active polymers having asymmetric silicon atoms in the main chain [17–
20]. There have not been many efforts made to create an optically active
hyperbranched system [21,22] in contrast to the precisely constructed opti-
cally active dendrimers. Optically active hyperbranched polymers prepared
by an one-pot polymerization of optically active monomer allow the intro-
duction of optical active units and functional groups to the interior and
terminal of the molecules which may lead to efficient asymmetric catalysts
or chiral recognition materials.
RESULTS AND DISCUSSION
Poly(silphenylene-siloxane)
Silphenylene-siloxane polymers have been generally synthesized by
homocondensation reaction of phenylene disilanol or heterocondensation
of disilanol with suitable difunctional silane or siloxane. When considering
the preparation of monomer and removal of byproducts with ease, the
silanol-aminosilane condensation polymerization is the best choice for its
high efficiency. The synthesis of monomers and polymers are shown in
Schemes 1 and 2. When preparing 1,4-bis(methylchlorosilyl)benzene, the
reaction was controlled to proceed at around room temperature within a
relatively short reaction time in order to minimize the unexpected dispro-
portionation reaction of the silane derivatives. By using slightly excessive
amount of water in the palladium-catalyzed dehydrocoupling polymeriza-
tion of BSB with water, the prepolymer 3a with hydroxy terminal and
narrow polydispersity (Mn ¼ 2840, PD ¼ 1.03) was obtained.
The exactly alternating structure of –(CH3)2Si-Ph-Si(CH3)2-O– (TMPS)
and functional group substituted –(R)(CH3)Si-Ph-Si(R)(CH3)-O– (RMPS,
R ¼ H or Vi) units in polymer structure was confirmed by NMR. 29Si NMR
of PH25-alt shows only two sharp singlets at ꢁ13.73 ppm and 0.86 ppm
due to the two kinds of backbone silicon atoms, methylhydridosilylene
and dimethylsilylene, and PV25-alt presents two sharp singlets at
ꢁ12.76 ppm and ꢁ0.40 ppm corresponding to methylvinylsilylene and
dimethylsilylene respectively. PV25-ran shows two sets of signals at
ꢁ0.38, ꢁ1.25, and ꢁ12.01, ꢁ12.76 ppm (Fig. 1). The signals at ꢁ0.38 and
ꢁ12.76 ppm are reasonably assigned to the dimethylsilylene and methyl-
vinylsilylene in the disiloxane linkages of the alternating cross diad units
in PV25-ran. The signals at ꢁ1.25 and ꢁ12.01 ppm are obviously generated
by the dimethylsilylene and methylvinylsilylene in their homo diad units in
the random building blocks.
Polymerization of prepolymer 3a with diethylamino-functionalized
monomers led smoothly to give polymers with hydrido or vinyl function,

78
Y. Kawakami et al.
SCHEME 1 Syntheses of bis(silyl)benzenes (1, 2) and prepolymers (3).
which have another alternating structure of chain segment–[(CH3)2Si-Ph-
Si(CH3)2-O]n– and RMPS unit. The functional units, RMPS, are very well
dispersed in the polymer chain. 29Si NMR of both polymers show one major
peak of -Me2Si- (at ꢁ1.26 ppm for PH and ꢁ1.17 ppm for PV and two minor
peaks corresponding to -MeRSi- (at ꢁ13.82 ppm for PH and ꢁ12.71 ppm
for PV) and -Me2Si- (at 0.86 ppm for PH and ꢁ0.33 ppm for PV) which
is adjacent to -MeRSi-.
Deaminative polycondensation of 2c with bis(aminosilane)s 1a or 1b
also proceeded smoothly to give polymers PV50-alt and PV75-alt, in which
vinyl contents are 50% and 75% respectively. Similar to PV25-alt,
these polymers have very defined exactly alternating structures from the
disilanol and bis(aminosilane) components. The disilanol 2b derived from
1,4-bis(methylvinylchlorosilyl)benzene did self-condensation quickly to
form a mixture of silanol-terminated oligomer 3b. Employing this oligo-
disilanol 3b to the further dehydrative polycondensation catalyzed by

High Performance Siloxane-Containing Polymers
79
SCHEME 2 Polymerization of 1-3.
n-hexylamine-2-ethylhexonate, polymer PV50-homo containing 50% vinyl
substituent was obtained in good yield. Similarly, n-hexylamine-2-ethylhexo-
nate catalyzed dehydration of disilanol 2c was also successful to give fully-
vinyl substituted PV100.
All polymers have glass transition temperatures (Tg) ranging from
ꢁ22ꢂC to ꢁ52ꢂC, which are relatively lower than ambient temperature.
Compared with PTMPS, introducing hydride and vinyl functions to the
polymer side chain has not only diminished the crystallinity, but also
decreased the glass transition temperature. DSC measurement of polymers
PH and PV revealed that the Tgs of them are about 10ꢂC higher than PH25-
alt and PV25-alt and partial crystallization occurred at 11ꢂC for PH and
23ꢂC for PV. The Tgs and Tcs are very similar to that of PTMPS (Tg ¼
ꢁ22ꢂC, Tc ¼ 15ꢂC). The lowest Tg was given by PV50-homo, in which every
silicon atom in the backbone is an asymmetric center. The existence of
asymmetric center and vinyl side group should be the reason of disappear-
ance of crystallinity and the decrease of Tg.
TGA curves of polymers under nitrogen atmosphere are shown in Figure 2.
It can be seen that a single-step process occurred for degradation in
nitrogen, while a multi-step process involved in air. Each polymer has an
onset degradation temperature above 400ꢂC, and an end temperature of
major degradation higher than 600ꢂC, except for PH25-alt. Compared to
PTMPS, there is a dramatic increase of the residue yield for both SiH-
substituted PH25-alt and vinyl-substituted PV25-alt and PV25-ran, even
for PV just containing a very low percentage of vinyl content. PV25-ran
shows the almost same degradation behavior with PV25-alt, but its weight
loss at the end is 6% more than PV25-alt. This slight decrease of thermal

80
Y. Kawakami et al.
FIGURE 1 29Si NMR spectra of vinyl containing polymers.
stability of PV25-ran may be caused by its random structure and relative
low molecular weight. It can be seen that introducing SiH functions made
the polymer PH25-alt produce the highest residue yield, although it
showed a lower initial temperature of degradation. Compared with
PTMPS, the onset degradation of all polymers containing high contents
of vinyl substituents was shifted to higher temperature, and the residual
yields were significantly increased. The data of all dynamic and isothermal
TGA were summarized in Table 1. It can be seen that the Td at 5% weight
loss and residual yield in nitrogen seemed to increase as a function of the
increase of vinyl content. Introducing 25% vinyl groups has elevated the Td
in nitrogen to 498ꢂC from 431ꢂC of PTMPS, and the residue yield increased
to 67% compared with 36% of PTMPS. PV50-homo and PV50-alt showed
their degradation curve quite similarly and ended at a same 83% residue
yield. Fully vinyl-substituted PV100 lost 5% weight at 611ꢂC and only
10% when heated to 1000ꢂC, which was undoubtedly the most thermally
stable.
In air (Fig. 3), it is clear that the major weight loss step of the functio-
nalized polymers moved to higher temperatures compared to PTMPS. All
polymers containing functional side groups show the temperature of 50%
weight loss well above 600ꢂC, and final residues higher than that of

High Performance Siloxane-Containing Polymers
81
FIGURE 2 TGA curves of all phenylene-disiloxane polymers measured under
nitrogen.
TABLE 1 Characteristics of all Phenylene-Disiloxane Polymers.
Residue at
Td,onset [ꢂC] 1000ꢂC [%]
d
Vinyl
content
[%]
Repeating
unitsa
ꢂ
Mw Mw=Mn Tgc[ C] in N2 in air in N2 in air
b
b
Polymers
PTMPS
PV25-alt
PV25-ran
PV50-alt
PV-50-homo
PV75-alt
PV-100
PV
—MM—
—MM—VM—
0
20,100 1.52
ꢁ22 431 387
ꢁ33 498 521
ꢁ40 475 481
ꢁ32 541 515
ꢁ52 553 548
ꢁ47 583 524
ꢁ45 611 582
ꢁ24 460 499
ꢁ38 345 362
ꢁ23 407 388
36
67
61
83
83
88
90
48
68
40
31
54
44
56
58
60
79
47
57
38
25 31,300 2.92
4,700 1.30
—MM—(ran)—VM ꢃ25
—MM—VV—
—VM—
50 88,700 4.73
50 72,700 4.85
75 37,100 3.60
100 57,400 3.58
<5 39,800 1.83
69,300 2.97
—VM—VV—
—VV—
—(MM)m—VM—
—MM—HM—
—(MM)m—HM—
PH25-alt
PH
39,500 2.21
a MM ¼
, VM ¼
, VV ¼
, HM ¼
.
bEstimated by GPC with polystyrene standard.
cDetermined by DSC analysis.
dTemperature of 5% weight loss.

82
Y. Kawakami et al.
FIGURE 3 TGA curves of all phenylene-disiloxane polymers measured in air.
PTMPS. Consistent with the result in nitrogen, polymers of alternating
structure (PH25-alt and PV25-alt) have higher stability than that of PH,
PV, or PV25-ran. After undergoing a complicate multi-step degradation
process, the residue of every polymer is white hard solid, which looks quite
different from the black residue of degradation in nitrogen. The white resi-
due is considered to be silica formed from the thermo-oxidative degrada-
tion in air, but the black one in nitrogen is still unsure in detail.
The TGA carried out in air indicated that the thermo-oxidative stability
was also greatly improved by introducing thermally vulcanizable vinyl side
functions. The most stable PV100 with 100% vinyl content had its Td elev-
ated to 582ꢂC and gave 79% residue at 1000ꢂC. These dynamic TGA results
proved the poly(silphenylenesiloxane)s with high vinyl-content have
maintained interesting thermal stability to about 500ꢂC and surprisingly
high residue yields even to 1000ꢂC.
Polysilsesquioxanes
Pd2(dba)3, reported as an efficient catalyst for the cross-dehydrocoupling
polymerization, gave only low molecular weight oligomers in 2 h
(Mw=Mn ¼ 3,330=750). After 42 h, the molecular weight of the product
increased, but apparent molecular weight distribution became very broad

High Performance Siloxane-Containing Polymers
83
with roughly bimodal distribution (Mw=Mn ¼ 21,400=1,750). The lower
molecular weight fraction could be removed by reprecipitation into etha-
nol=hexane. The insoluble fraction was proved to be a high molecular
weight polymer (Mw=Mn ¼ 62,200=25,400).
1H NMR spectrum of polymer showed two broad signals at around 2.70–
3.60, and 6.40–7.80 ppm, which are ascribed to hydroxyl and phenyl pro-
ton. 29Si NMR spectrum, in Figure 4, exhibited main signals at ꢁ79.1
ꢁ70.45, and ꢁ67.97 ppm, which are assigned to PhSi(O-)3 (T3), PhSi(O-)2
OH (T2) and PhSi(O-)(OH)2 (T1) structure, [23] respectively. The area
ratio is roughly 60 : 31 : 9. The fact that the polymer is soluble in common
organic solvent strongly suggests that the polymer has only small amounts
of cross-linking even with about 60% of T3 structure.
The progress of the polymerization was monitored by SEC (exclusion
limit Mn ¼ 4.0 ꢄ 105). After 30 seconds, the molecular weight of the pro-
duct is low with narrow molecular weight distribution. PhSi(Me3SiO)3,
PhSiH(Me3SiO)2,(Me3SiO)2PhSiOSiPhH(OSiMe3, {(Me3SiO)2PhSi}2O, and
{(Me3SiO)PhSiO}3 were isolated among the products in the initial stage,
after capping the products with Me3SiCl. These compounds should be
formed from phenylsilanediol (6) and phenylsilanetriol (7). It should be
stressed that no phenylsilane (4), nor phenylsilanol (5) was detected in
the reaction system. This fact suggests that hydrolysis of SiH function with
water by Pd catalyst is fast in the very early stage of the reaction, and that
the first and second silane functions are more reactive than the third silane
function toward hydrolysis. Cross-dehydrocoupling reaction between SiH
FIGURE 4 29Si NMR spectrum of polysilsesquioxane obtained by dehydrogentaive
polycondensation of phenylsilane and water.

84
Y. Kawakami et al.
and SiOH functions of these compounds seems responsible for the faster
consumption of SiH functions. Dehydration reaction is a relatively slower
process compared with the reactions which consume SiH function as
reported in synthesis of siloxane-arylene polymer from bis(silane) with
water.
In 29Si NMR after 15 minutes, basically five kinds of signals were
observed at around ꢁ78.4, ꢁ70.5, ꢁ67.4; ꢁ65.9, ꢁ62.8; ꢁ60.7, and
ꢁ47.5 ppm. The signal at ꢁ78.4 ppm is assigned to T3, and that at ꢁ70.5
to T2. The signals at ꢁ67.4; ꢁ65.9 ppm are assigned mainly as T1, respect-
ively. Sharp signals at ꢁ62.8; ꢁ60.7 ppm are reasonably considered to
originate from T2 of low molecular weight products, for example, cyclic
structure like cyclotrisiloxane. The signal at ꢁ47.5 ppm might be assigned
to PhSi(O-)2H(DH). In the signal after 30 seconds, the major peaks are
observed at ꢁ78.5, ꢁ70.2, and ꢁ47.4 ppm. It should be stressed that in
the very early stage of the polymerization, the species present in the sys-
tem are, T3, T2, and DH and only small amounts of T1 present. After
15 min, the signal of DH almost disappeared, and instead, the signals of
T2 and T1 (ꢁ70.5, ꢁ62.8; ꢁ60.7 and ꢁ67.4; ꢁ65.9 ppm) and T3
(ꢁ78.4 ppm) became stronger. The signals at ꢁ62.8; ꢁ60.7 and ꢁ67.4;
ꢁ65.9 ppm assignable to T2 and T1decreased gradually with reaction time
after taking maximum, and became weak after 42 h. Especially the change
of T2 assignable to low molecular weight products is notable. The signal of
T2 at ꢁ70.5 ppm became stronger and broader with reaction time, and that
of T3 also became stronger. After 42 h, the peak of T3 became the strongest.
The major structure of polymer is consisted of T2 and T3 structure.
The solubility in organic solvent and the ratio of T1, T2 and T3 strongly
suggest non cross-linked structure of the polymer having cyclic moiety as
shown in Scheme 3. Polymer can be cast into a transparent rather fragile
film. This polymer may find an application as a coating material.
The mass was lost gradually (8.5%) in thermo-gravimetric analysis
(TGA) in air from room temperature through at around 500ꢂC, presumably
because of elimination of water by condensation of SiOH of T2 structure. In
IR spectrum of the residue at 500ꢂC, the absorption of OH (3369 cmꢁ1) was
disappeared. The weight loss was observed at around 510ꢂC, which was
caused by the removal of phenyl group. The residual weight of 46.7% is
close to the expected value, 46.5%, calculated based on the assumption
that all the Si is oxidized to SiO2 [24].
Siloxane Gel
Siloxane gels were prepared by deamination reaction as shown in
Scheme 4. In the early stage, the polymer has low molecular weight but
with narrow molecular weight distribution (10, 20 min). After 30 min, a

High Performance Siloxane-Containing Polymers
85
a
SCHEME 3 Plausible mechanism of polymerization. Not isolated. Concentration
b
of SiH is very low.

86
Y. Kawakami et al.
SCHEME 4 Synthesis of siloxane gel and polysiloxanes.
shoulder peak of cyclic compounds appeared, and after 1 hr, the molecular
weight of the products increased (Mw as high as 350,000 (polystyrene
standard)) and polydispersity became wide. After about 3 hr, the reaction
mixture became insoluble.
After 10 min in 29Si NMR, the signal of monomer (should be observed at
ꢁ22.77 ppm) already disappeared completely, and the signals of cyclic
compounds were observed at around ꢁ31 ppm (five peaks ꢁ31.12,
ꢁ30.92, ꢁ30.85, ꢁ30.76 ppm) and at ꢁ20.91 ppm (apparent singlet),
respectively. The peak at ꢁ21.09 ppm next to the signal of cyclic compound
is considered to originate from MePhSi(O-)OH of chain end. The peak at
ꢁ26.09 ppm might be ascribed to intermediately formed MeSi(O-)
(NMe2)2, in which one amino group of 9a condenses with silanol. The sig-
nal seen at around ꢁ31.5 ppm is considered assignable to cyclic structure in
the polymer, which was formed by condensation of amino group in polymer
chain with silanol function of chain end. The major signal at ꢁ33.72 ppm is
assigned to MePhSi(O-)2 of disiloxane unit in the polymer, and the signal at
ꢁ66.95 ppm, which appeared after 30 min and became strong with reaction
time ([MeSi(O-)3]=[MePhSi(O-)2] ¼ 1=6.9 (1 hr), 1=5.4 (2 hr)), is assigned
to MeSi(O-)3 of cross-linking unit. The signal at around –57 ppm is con-
sidered as MeSi(O-)2NMe2 or MeSi(O-)2OH in which two amino groups
of 9a condense with silanol, or amino group of MeSi(O-)2NMe2 was hydro-
lyzed with H2O formed by self-condensation of 8. The GPC trace and 29Si
NMR analysis indicated that, in the early stage of the polymerization, cycli-
zation by self-condensation of 8 and oligomerization occurred. The first and
second amino group of 9a seems to have higher reactivity than that of the
third amino group. In the later part of the polymerization, branching
occurred by the reaction of the remaining third amino group with silanol
function to form hyperbranched structure, followed by the gradual cross-
linking to give insoluble siloxane gel [25].

High Performance Siloxane-Containing Polymers
87
Stereoregular Polysiloxane
Stereoregular polysiloxane was synthesized according to Scheme 5.
ipso-Carbon peaks (I ¼ 137.1, H ¼ 136.9, S ¼ 136.7ppm) showed defi-
nite splitting based on the triad tacticity. The triad tacticity of poly
(methylphenylsiloxane) prepared from (S,S)-8 and 10 [(S,S):(S,R):
(R,R)¼ 84:16:0] in the presence of Et3N was estimated as S:H:I ¼
60:32:8 from the ipso-carbon peaks [26].
SCHEME 5 Synthesis of syndiotactic poly(methylphenylsiloxane) (PMPS).
Optically Active Siloxane Gel
Polycondensation of (S,S)-8 with bis(dimethylamino)dimethylsilane 9b or
bis(dimethylamino)diphenylsilane 9c was carried out (Scheme 4), and the
results are summarized in Table 2.
The information about the regularity in the connection of the two suc-
cessive disiloxane units (stereoregularity) was obtained by the analysis
1
of H signals of SiMe2 sandwiched between (S or R)-PhMeSiꢀO and (S or
R)-OSiꢀMePh [(S or R)-Si and (S or R)-Si] in successive units. As a first
approximation, the two methyl groups should appear as a singlet when
sandwiched between two silicon atoms of the same absolute configuration,
and two singlets when sandwiched by two silicon atoms of opposite con-
figuration. There is only one possible combination of the configuration of
(S)-Si-SiMe2-(S)-Si for P1 from (S,S)-8, thus the methyl groups of the
P1 from (S,S)-8 gave basically a singlet. This polymer is considered to
be rich in (S,S)-diisotacticity together with the analysis of the stereo-
chemistry of the disiloxane unit.
24
The diisotactic P1 showed the positive optical rotation ([a]D ¼ þ 2.3,
24
entry 1), whereas that of diisotactic P2 showed negative optical rotation
([a]D ¼ ꢁ2.0, entry 4) [27].
This reaction was applied for the synthesis of optically active siloxane
gels. The polycondensation reaction of phenylsilane and (S,S)-1,3-
dimethyl-1,3-diphenyldisiloxane-1,3-diol gave the poly(silsesqioxane) with
molecular weight (Mn) 15,000 (purified by repeated reprecipitation into
MeOH) by GPC (exclusion limit Mn ¼ 4.0 ꢄ 105), when the reaction was
27
stopped after 2 hr. This polymer showed optical activity ([a]D ¼ ꢁ1.77
(c ¼ 1.25, CHCl3)), which is considered to be induced by the asymmetric
silicon atoms of (R,R)-8 unit in the polymer structure. The polymer is

88
Y. Kawakami et al.
TABLE 2 Synthesis of Optically Active Polysiloxanes via Polycondensation of 8
with 9
Yield [%]d Mn
Mw=Mn [a]D
Tg[ꢀC]h
e
e
24
Entry
8
9
Polymer
1
2
3
4
5
6
(S,S)a
a
a
a
b
b
b
(S,S)-diisotactic P1
meso-atactic P1
atactic P1
48
49
65
53
38
51
51,200
50,300
74,300
18,400
43,800
49,100
1.85
2.10
1.51
2.86
2.18
1.70
þ 2.3f
ꢂ2.0g
ꢂ56
ꢂ53
ꢂ54
ꢂ2
mesob
diastereomerc
(S,S)a
(R,R)-diisotactic P2
meso-atactic P2
atactic P2
mesob
ꢂ10
ꢂ11
diastereomerc
a(S,S) : (S,R) : (R,R) ¼ 86 : 14 : 0.
bPure isomer.
c(S,S) : (S,R) : (R,R) ¼ 25 : 50 : 25.
dIsolated yields after reprecipication into methanol.
eEstimated by GPC (THF as an eluent) with polystyrene standard.
fc ¼ 0.870, CHCl3.
gc ¼ 0.820, CHCl3.
hDetermined by DSC with heating rate of a 5ꢀC minꢂ1 on second scan.
considered to have potential applications as enantiorecognitive separating
membrane or chiral column packing materials.
Optically Active Hyperbranched Polymer
Hydrosilylation polymerization reactions with various feed ratio of (S,S)-11
(AB2 monomer) and 12 (A‘B’ monomer) were carried out in bulk at 60–
80ꢀC for 12 h in the presence of 0.1 mol% of Pt(0)(DVTMDS)2 to give opti-
cally active hyperbranched polymers with chain end Vi functional groups
(Table 3). The existence of Si-H groups in P3 was confirmed by means
1
of H NMR (4.51 ꢁ 4.83 ppm, [Si-H] : [Vi] ¼ 1 : 9) and IR (2154 cmꢂ1).
Apparent degree of polymerization (DP) for P3 is calculated as about 8
(clacd.Mn ¼ 4,700), which agrees with the Mn (¼ 4,320) determined by
VPO.
The information about the branching structures for P3 was obtained by
29Si NMR analysis of –CH2CH2SiMe(O–)2 signals at ꢂ20.1, ꢂ18.6, and
ꢂ17.9 ppm which reflect the branching structures such as dendritic (D),
terminal (T), and linear (L) [28] units as shown in Figure 5. Assignment
was done using model compounds. The relative percentages of each
branching silicon atom can be determined from these signals of the T
(ꢂ17.9 ppm), D(–20.1 ppm), and L(ꢂ18.6 ppm) units in P3, respectively.
The relative percentage of T : L : D in P3 is found to be 20 : 57 : 23.
The degree of branching (DB) of hyperbranched polymers is defined as
follows;

High Performance Siloxane-Containing Polymers
89
TABLE 3 Polymerization Reactions with Various Feed Ratio of (S,S-11 and 12
þ
ꢁ! hyperbranched polymer
Polym.
comp.
[%]d Mn Mw=Mn (S,S)-11:12 DBobsd. DBcalcd. [a]D
Feed ratio
Yield
Tg
[ꢂC]
e
e
24
Entry (S,S)-11:12
Polymer
1
2
3
4
5
6
7
100:0
100:0
66:34
50:50
34:66
25:75
0:100
meso=DL-P3 90 3,970
1.8
2.1
2.4
2.5
3.2
3.6
1.8
100:0
100:0
63:37
49:51
33:67
26:74
0:100
0.45
0.43
0.38
0.35
0.31
0.27
0.50
26
P3
P4
P5
P6
P7
P8
87 4,320
89 4,530
86 6,240
82 6,850
72 9,370
71 4,700
0.50 þ13.1
34
22
10
0.48
0.44
0.38
0.32
þ9.8
þ8.3
þ5.9 ꢁ12
þ4.5 ꢁ29
ꢁ49
aIsolated yields after reprecipication into methanol.
bEstimated by GPC (THF as an eluent) with polystyrene standard.
T þ D
DBAB2
¼
T þ L þ D
P4 ꢃ P7 showed the optical rotation [a] with the same positive sign as the
(S,S)-11 used for polymerization. This is in accordance with the expec-
tation that in hydrosilylation polymerization proceeded with 100% reten-
tion of configuration, in which chiral silicon center remains unaffected.
The absolute value of [a] (13.1ꢂ ) observed for P3 having 14 ꢃ 16 chiral
silicon atoms is higher than that of monomer (6.9ꢂ ) [28].
FIGURE 5 Possible branching structures of P3 and their 29Si NMR chemical shifts
of Si.

90
Y. Kawakami et al.
EXPERIMENTAL
General
NMR (1H, 500 MHz; 13C, 125.5 MHz; 29Si, 99.5 MHz) spectra were obtained
in CDCl3 on a Varian UNITY INOVA. Chemical shifts are reported in ppm
relative to internal CHCl3 (7.26) for 1H, CDCl3 (77.00) for 13C, and external
tetramethylsilane (0.00) for 29Si. Solid state NMR (13C, 100.4 MHz; 29Si,
79.6 MHz) spectra were obtained on a 400 MHz UNITY INOVA. Chemical
shifts are reported in ppm relative to external hexamethylbenzene (d
17.30) for 13C CP MAS, and tetramethylsilane (d 0.00) for 29Si MAS. IR
spectra were obtained on a JASCO VALOR-III spectrophotometer. GC
and DI EI-Mass analyses (MS) were carried out on a Shimadzu QP-5000
mass spectrometer. High-resolution electrospray ionization mass (HRE-
SIMS) analyses were carried out on a Bruker DALTONICS Bio-Apex 70 E
mass spectrometer. Specific optical rotations were measured with a JASCO
DIP-370S digital polarimeter. Size exclusion chromatography (SEC)
and HPLC analyses were performed on a JASCO HPLC model Gulliver
900 with combinations of Shodex KF-801 and KF-802 (exclusion limit
Mn ¼ 5.0 ꢄ 103), KF-803L and KF-804 (exclusion limit Mn ¼ 4.0 ꢄ 105),
and KF-805L and KF-806L (exclusion limit Mn ¼ 2.0 ꢄ 107) using tetrahy-
drofuran as an eluent (flow rate, 1 ml=min), and on a Daicel Chem. Ind.,
CHIRALCEL1 OD [cellulose tris(3,5-dimethylphenylcarbamate)] optically
active stationary phase using n-hexane as an eluent (1 ml=min). Vapor
pressure osmometry (VPO) analysis was performed on a CORONA ELEC-
TORIC CO., Ltd. Model 114 using benzene as solvent. Differential scanning
calorimetric (DSC) analysis was performed on a Seiko DSC6200 instrument
at a heating rate of 5.0ꢂC=min under nitrogen flow. Thermogravimetric
analysis (TGA) was performed on a Seiko Instruments TGA=DTA 220 with
a heating rate of 5.0ꢂC=min under nitrogen flow or in air.
Materials
Details of the information on the reagents and procedures used in this
report can be obtained from references published.
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