Synthesis and characterization of poly(carbonates) and poly(thiocarbonates) derived from diphenols containing silicon as central atom

Article abstract of DOI:10.1080/104265090970089

Poly(carbonates) and poly(thiocarbonates) containing silicon in the main chain and derived from the diphenols bis(4-hydroxyphenyl)-dimethylsilane, bis(4-hydroxyphenyl)-ethylmethylsilane, and bis(4-hydroxyphenyl)-diethylsilane with phosgene or thiophosgene

Full text of DOI:10.1080/104265090970089

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Phosphorus, Sulfur, and Silicon
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Synthesis and Characterization
of Poly(carbonates) and
Poly(thiocarbonates) Derived
from Diphenols Containing
Silicon as Central Atom
L. H. Tagle a , C. A. Terraza a & P. Alvarez a
a Facultad de Química , Pontificia Universidad
Católica de Chile , Santiago, Chile
Published online: 16 Aug 2006.
To cite this article: L. H. Tagle , C. A. Terraza & P. Alvarez (2006) Synthesis and
Characterization of Poly(carbonates) and Poly(thiocarbonates) Derived from Diphenols
Containing Silicon as Central Atom, Phosphorus, Sulfur, and Silicon and the Related
Elements, 181:2, 239-248, DOI: 10.1080/104265090970089
To link to this article: http://dx.doi.org/10.1080/104265090970089
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Phosphorus, Sulfur, and Silicon, 181:239–248, 2006
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/104265090970089
Synthesis and Characterization of Poly(carbonates) and
Poly(thiocarbonates) Derived from Diphenols Containing
Silicon as Central Atom
L. H. Tagle
C. A. Terraza
P. Alvarez
Facultad de Qu´ımica, Pontificia Universidad Cato´lica de Chile,
Santiago, Chile
Poly(carbonates) and poly(thiocarbonates) containing silicon in the main chain
and derived from the diphenols bis(4-hydroxyphenyl)-dimethylsilane, bis(4-
hydroxyphenyl)-ethylmethylsilane, and bis(4-hydroxyphenyl)-diethylsilane with
phosgene or thiophosgene, respectively, were synthesized under phase transfer con-
ditions, using several phase transfer catalysts. Polymers were characterized by spec-
1
13
29
troscopic methods (IR and H, C, Si NMR) and the results were evaluated
by the yields and the η values. In general the effectiveness of the phase trans-
inh
fer process was low, the best results being obtained when the NaOH concentra-
tion was increased from the stoichiometric due to a salting-out effect. However,
at higher concentrations hydrolytic process were observed. Poly(carbonates) and
poly(thiocarbonates) showed, in general, the same trend with the catalysts.
Keywords Poly(carbonates); poly(thiocarbonates); phase transfer catalysis; silicon con-
taining polymers
INTRODUCTION
Silicon-containing condensation polymers have been studied widely, be-
cause they present scientific and technological interest due to the po-
tential applications for the production of optical and electronic mate-
rials. In this sense, several kinds of condensation polymers containing
Si as part of the main chain have been described, such as poly(esters),
poly(carbonates), poly(amides), and others. Normally the Si atom is
bonded to two aromatic rings and two other aliphatic or aromatic ones,
Received November 11, 2004; accepted February 7, 2005.
The authors acknowledge the financial support of FONDECYT through grant
1030528.
Address correspondence to L. H. Tagle, Pontificia Universidad Cato´lica de Chile, Fac-
ultad de Qu´ımica, P.O. Box 306, Santiago, Chile. E-mail: ltagle@puc.cl
239

240
L. H. Tagle et al.
with the poly(silylene) moities having the general form -Ar-Si(R1R2)-Ar-
R1 and R2 being aromatic or aliphatic groups.1−3
In our research group we have focussed our attention on the synthe-
sis of condensation polymers using the phase transfer catalysis tech-
nique. This technique permits the transfer of a diphenolate dianion as
an ionic pair with the catalyst from the aqueous phase to the organic
one, in which the reaction takes place. In this sense we have synthe-
sized several kinds of condensation polymers such as poly(carbonates),
poly(thiocarbonates), and poly(esters) and studied the effect of the na-
ture of the catalyst in the yields and inherent viscosity (ηinh). We have
shown that this technique is a very useful tool for the synthesis of these
polymers.4
In the last years we have applied the phase transfer catalysis
to the synthesis of condensation polymers derived from monomers,
diphenols, or acid dichlorides, containing Si or Ge, in order to obtain
poly(carbonates), poly(thiocarbonates), and poly(esters) containing one
or two of these heteroatoms.5,6 We have observed that when the NaOH
concentration is increased in the aqueous phase, it is possible to see a
salting-out effect of the diphenolate to the organic phase, which has, as
a consequence, an increase of the yields and in some cases of the molecu-
lar weights. This is due to the increase of the concentration that can dis-
place the equilibrium to the diphenolate formation. On the other hand,
it was also possible to see hydrolytic effects of both the monomer and
the polymeric chains. In addition, we have synthesized poly(urethanes)
containing Si or Ge by interphasial condensation.7
In this work we describe the synthesis and characterization of
poly(carbonates) and poly(thiocarbonates) derived from diphenols con-
taining Si as the central atom bonded to two aliphatic groups and phos-
gene or thiophosgene, respectively. We studied the qualitative behavior
of the phase transfer catalysts and the increase of the NaOH concen-
tration through the yields and the (ηinh) of the obtained polymers.
EXPERIMENTAL
Reagents and solvents (from Aldrich or Riedel de Haen) were used with-
out purification. The following catalysts (from Fluka) were used: Tetra-
butylammonium Bromide (TBAB), Benziltriethylammonium Chloride
(BTEAC), and Methyltrioctylammonium Chloride (ALIQUAT 336). The
IR spectra were recorded on a Perkin-Elmer 1310 spectrophotometer
1
and the H, 13C, and 29Si NMR were recorded on a 400 MHz instru-
ment (Bruker), using CDCl3, acetone-d6, or DMSO-d6 as solvents and
TMS as the internal standard. Viscometric measurements were made
in a Desreux–Bischoff8 type dilution viscosimeter at 25◦C.

Poly(carbonates) and Poly(thiocarbonates)
241
Diphenols
The diphenols bis(4-hydroxyphenyl)-dimethylsilane, bis(4-hydroxy-
phenyl)-ethylmethylsilane, and bis(4-hydroxyphenyl)-diethylsilane,
were synthesized from p-bromo-phenol and dimethyl-, ethylmethyl-
or diethyl-dichlorosilane, according to the procedure described by
Davidson et al.,9 in which 14.1 g (0.08 mol) of p-bromophenol in THF
were added under N2 to 75 mL of n-butyllithium (2.5 N solution in n-
hexane) at –70◦C. Then, the temperature was increased slowly until 5◦C
and the mixture was stirred for 1 h. The temperature was decreased to –
50◦C and 0.025 mol of dimethyl-, ethylmethyl-, or diethyl-dichlorosilane
were added in THF, and the temperature increased until 10◦C and was
stirred for 2 h. The mixture was hydrolyzed by adding 5% HCl until
obtaining a yellow mixture (pH 1). The organic layer was dried under
MgSO4 and the solvent evaporated. The brown oil was poured into n-
hexane obtaining a white solid, which was recrystallized from toluene
and characterized.
Bis(4-hydroxyphenyl)-dimethylsilane: m.p: 170–171◦C (Lit.8 173–
174◦C). I.R. (KBr) (cm−1): 3319 (OH), 3020 (H arom.), 2958, 2871 (CH3),
1598, 1500 (C C arom.), 1457 (CH3), 829 (arom. p-subst.). 1H NMR (δ)
(ppm) (acetone-d6) 0.45 (s, 6H, CH3), 6.84 (d, 4H, arom), 7.35 (d, 4H,
arom), 8.41 (s, 2H, OH). 13C NMR (δ) (ppm) (acetone-d6): −1.36 (CH3-Si),
116.2, 129.2, 136.8, 159.6 (arom.) 29Si NMR (δ) (ppm) (CDCl3): −9.36.
Bis(4-hydroxyphenyl)-ethylmethylsilane: m.p.: 138–140 ◦C. I.R.
(KBr) (cm−1): 3314 (OH), 3026 (H arom.), 2954, 2874 (CH3), 2912 (CH2),
1600, 1503 (C C arom.), 1459 (CH3), 831 (arom. p-subst.). 1H NMR (δ)
(ppm) (acetone-d6): 0.51 (s, 3H, CH3-Si), 1.47 (m, 5H, CH2-CH3), 6.92
(d, 4H, arom.), 7.42 (d, 4H, arom.), 8.47 (s, 2H, OH). 13C NMR (δ) (ppm)
(acetone-d6): -4.00 (Si-CH3), 7.40 (CH2-CH3), 8.25 (CH2-CH3), 116.3,
128, 137.1, 159.6 (C arom.). 29Si NMR (δ) (ppm) (CDCl3): -6.93.
Bis(4-hydroxyphenyl)-diethylsilane: m.p.: 77–78◦C. I.R. (KBr)
(cm−1): 3330 (OH), 3055 (H arom.), 2960, 2878 (CH3), 2935 (CH2), 1599,
1502 (C C arom.), 1456 (CH3), 821 (arom. p-subst.). 1H NMR (δ) (ppm)
(CDCl3): 0.97–1.03 (m, 10H, CH2-CH3), 4.64 (s, 2H, OH), 6.84 (d, 4H,
arom.), 7.38 (d, 4H, arom.). 13C NMR (δ) (ppm) (CDCl3): 4.23 (CH3), 7.42
(CH2), 114.9, 127.6, 136.6, 156.4 (C arom.). 29Si NMR (δ) (ppm) (CDCl3):
−4.83.
Poly(carbonates) and Poly(thiocarbonates)
The poly(carbonates) and poly(thiocarbonates) were synthesized ac-
cording to the following general procedure: the diphenol (1 mmol) was
dissolved in 0.5 M NaOH and water (total volume 15 mL), and then

242
L. H. Tagle et al.
15 mL of CH2Cl2 and the catalyst (5% in mol) were added. To this
mixture, 1 mmol of phosgene (from a toluene solution) or thiophosgene
was added and the mixture stirred at 20◦C for 1 h. After this time, the
organic layer was poured into 300 mL of methanol and the polymer
was filtered, washed with methanol, dried until constant weight, and
characterized.
Poly(carbonate) Ia
I.R. (KBr) (cm−1): 3020 (H arom.), 2958, 2871 (CH3), 1774 (C O),
1
1598, 1500 (C C arom.), 1457 (CH3), 829 (arom. p-subst.). H NMR
(CDCl3) (δ): 0.57 (s, 6H, CH3), 7.29 (d, 4H, arom.), 7.57 (d, 4H, arom).
13C NMR (CDCl3) (δ): -2.19 (Si-CH3), 115.0, 120.0, 135.6, 136.0 (arom.),
151.9 (C O). 29Si NMR (CDCl3) (δ): −7.46.
Poly(thiocarbonate) Ib
I.R. (KBr) (cm−1): 3022 (H arom.), 2957, 2873 (CH3), 1598, 1501 (C C
arom.), 1457 (CH3), 829 (arom. p-subst.). 1H NMR (CDCl3) (δ): 0.59 (s,
6H, CH3), 7.22 (d, 4H, arom.), 7.61 (d, 4H, arom.). 13C NMR (CDCl3)
(δ): -2.24 (Si-CH3), 120.6, 121.3, 135.6, 136.6 (arom.), 194.1 (C S). 29Si
NMR (CDCl3) (δ): −7.34.
Poly(carbonate) IIa
I.R. (KBr) (cm−1): 3027 (H arom.), 2956, 2875 (CH3), 2910 (CH2), 1775
(C O), 1590, 1497 (C C arom.), 812 (arom. p-subst.). 1H NMR (CDCl3)
(δ): 0.5 (s, 3H, CH3), 0.97–1.01 (m, 5H, CH2-CH3), 7.23 (d, 4H, arom.),
7.50 (d, 4H, arom). 13C NMR (CDCl3) (δ): -4.77 (Si-CH3), 6.01 (Si-CH2),
7.37 (CH2-CH3), 120.4, 135.1, 135.9, 151.7 (arom.), 151.7 (C O). 29Si
NMR (CDCl3) (δ): −5.11.
Poly(thiocarbonate) IIb
I.R. (KBr) (cm−1): 3029 (H arom.), 2955, 2875 (CH3), 2910 (CH2),
1
1586, 1494 (C C arom.), 811 (arom. p-subst.). H NMR (CDCl3) (δ):
0.63 (s, 3H, CH3), 1.08–1.14 (m, 5H, CH2-CH3), 7.28 (d, 4H, arom.),
7.65 (d, 4H, arom). 13C NMR (CDCl3) (δ): -4.77 (Si-CH3), 6.00 (Si-CH2),
7.37 (CH2-CH3), 120.4, 135.1, 135.9, 151.8 (arom.), 194.1 (C S). 29Si
NMR (CDCl3) (δ): −5.28.
Poly(carbonate) IIIa
I.R. (KBr) (cm−1): 3027 (H arom.), 2956, 2875 (CH3), 2910 (CH2),
1
1775 (C O), 1589, 1497 (C C arom.), 813 (arom. p-subst.). H NMR
(CDCl3) (δ): 0.98–1.02 (m, 6H, CH3), 1.06–1.11 (m, 4H, CH2), 7.27 (d,
4H, arom.), 7.53 (d, 4H, arom). 13C NMR (CDCl3) (δ): 4.0 (CH2), 7.3

Poly(carbonates) and Poly(thiocarbonates)
243
(CH3), 120.3, 134, 136.3, 152.4 (arom.), 152.4 (C O). 29Si NMR (CDCl3)
(δ): -3.55.
Poly(thiocarbonate) IIIb
I.R. (KBr) (cm−1): 3029 (H arom.), 2955, 2874 (CH3), 2934 (CH2),
1
1586, 1494 (C C arom.), 828 (arom. p-subst.). H NMR (CDCl3) (δ):
1.00–1.04 (m, 6H, CH3), 1.09–1.12 (m, 4H, CH2) 7.22 (d, 4H, arom),
7.58 (d, 4H, arom). 13C NMR (CDCl3) (δ): 3.97 (CH2), 7.38 (CH3), 121.2,
134.61, 136.2, 154.8 (arom.), 194 (C S). 29Si NMR (CDCl3) (δ): -3.55.
RESULTS AND DISCUSSION
Poly(carbonates) and poly(thiocarbonates) derived from the diphenols
bis(4-hydroxyphenyl)-dimethylsilane, bis(4-hydroxyphenyl)-ethylmet-
hylsilane and bis(4-hydroxyphenyl)-diethylsilane with phosgene or
thiophosgene, respectively, were synthesized under phase transfer con-
ditions using several phase transfer catalysts in CH2Cl2 as a solvent at
1
20◦C. Polymers were characterized by I.R. and H, 13C, and 29Si NMR
spectroscopy, and the results agreed with the following proposed struc-
tures (Scheme 1):
SCHEME 1
In all polymers it was possible to see the disappearance of the
OH band. In poly(carbonates) it was possible to see a new band at
1775 cm−1 corresponding to the C O of the carbonate group, and for
the poly(thiocarbonates) the increase of the intensity of the band at
1185 cm−1 corresponded to the C S group.
In this study the catalyst concentration, solvent, reaction time, and
temperature remained constant. Three base concentrations were stud-
ied, the molar ratios of NaOH/phenol being 2/1, 3/1, and 4/1, respec-
tively. The volume of the aqueous phase was the same in all cases
(15 mL). The efficiency of the catalysts was studied by measur-
ing the yields and inherent viscosity values (ηinh) of the obtained
polymers.
The reaction took place when the diphenolate dissolved in the aque-
ous phase was transferred to the organic one as an ionic pair due to the

244
L. H. Tagle et al.
action of the catalyst. For all the polymers, comparison experiments
without catalyst were made in order to evaluate the behavior of the
interphase of the system, with the observation that in some cases poly-
mers were obtained due to an interphasial polycondensation process
between the diphenolate dissolved in the aqueous phase and the phos-
gene or thiophosgene dissolved in the organic one. Three phase transfer
catalysts were used: TBAB, BTEAC, and ALIQUAT 336.
The choice of the catalysts was according to their structure. TBAB
has a symmetrical structure and has been described as adequate for
the synthesis of poly(carbonates) derived from analogous diphenols.10
BTEAC is a hydrophilic catalyst11 and adequate for the transportation
of more lypophilic diphenolates or with high organic content. On the
other hand, ALIQUAT 336 is a lypophilic catalyst due to the three n-
octyl chains bonded to the N atom, and is adequate for transporting
more hydrophilic diphenols or with a less organic content. In this study
the organic content of the diphenols is increased.
The increase of the NaOH concentration would displace the equilib-
rium to the diphenolate formation and also positively affect the transfer
process. However, the higher concentration of NaOH would increase the
possibility of hydrolysis of the phosgene or thiophosgene and of the poly-
meric chains, with a consequence of a decrease in the yields in the first
case, and in the molecular weights (ηinh) in the second.
Table I shows the results obtained for the poly(carbonate) Ia and
poly(thiocarbonate) Ib derived from the diphenol bis(4-hydroxyphenyl)-
dimethylsilane. For poly(carbonate) Ia the best results were surpris-
ingly obtained with BTEAC, which showed an increase of the yields
and the ηinh values when the NaOH concentration was increased.
This catalyst has been described as ineffective for the synthesis of the
poly(carbonate) derived from bisphenol A, which is analogous with this
diphenol, but when using a stoichiometric NaOH concentration.12 In
this case, the effectivity can be due to two factors. The first is the salting-
out effect of the diphenolate from the aqueous phase to the organic
one due to the increase of the NaOH concentration. The second can be
the absence of the hydrolysis of both the phosgene and the polymeric
chains, due to the effect of the catalyst. This catalyst has been described
as hydrophilic11 and consequently does not promote hydrolysis, which
has been described in the synthesis of other poly(carbonates).13 With
TBAB it is possible to see only a slight increase of the yields when the
NaOH concentration is increased to a 3:1 ratio, but at a ratio of 4:1, the
poly(carbonate) was not obtained. Probably in these cases there is hy-
drolysis of the phosgene and the polymeric chains. ALIQUAT 336, which
is a more lypophilic catalyst, hardly was effective at a stoichiometric
amount of NaOH due to the hydrolytic process. Without a catalyst, the

Poly(carbonates) and Poly(thiocarbonates)
245
TABLE I Yields and Inherent Viscosities Obtained for
Poly(carbonate) Ia and Poly(thiocarbonate) Ib Derived From the
Diphenol Bis(4-hydroxyphenyl)-dimethylsilane I, Poly(carbonate)
IIa, and Poly(thiocarbonate) IIb Derived From the Diphenol
Bis(4-hydroxyphenyl)-ethylmethylsilane II, and Poly(carbonate) IIIa,
and Poly (thiocarbonate) IIIb Derived From the Diphenol
Bis(4-hydroxyphenyl)-diethylsilane III
Catalyst
—
TBAB
ALIQUAT
BTEAC
∗∗
∗∗
∗∗
∗∗
%
Polymer
NaOH:phenol∗
%
η∗∗∗
%
η∗∗∗
%
η∗∗∗
η∗∗∗
Ia
Ia
Ia
Ib
Ib
Ib
IIa
IIa
IIa
IIb
IIb
IIb
IIIa
IIIa
IIIa
IIIb
IIIb
IIIb
2:1
3:1
4:1
2:1
3:1
4:1
2:1
3:1
4:1
2:1
3:1
4:1
2:1
3:1
4:1
2:1
3:1
4:1
—
59
5
—
0.25
—
38
0.16
0.16
—
0.08
0.28
0.13
—
0.12
0.12
—
0.08
0.14
—
17
0.13
—
—
0.08
0.21
0.13
—
0.16
—
35
0.16
0.44
0.50
0.04
—
59
—
14
73
30
—
53
21
—
73
73
9
15
21
—
32
6
—
—
16
73
56
—
43
—
—
83
84
4
2
2
—
15
10
79
79
7
—
31
57
—
27
20
—
41
47
2
—
—
—
20
2
—
0.18
0.13
—
0.11
0.14
—
0.14
0.14
—
—
—
—
0.08
—
—
—
44
39
—
42
12
6
68
71
46
71
61
54
—
0.11
0.10
—
—
0.10
0.07
0.09
0.14
0.15
0.10
0.11
0.16
0.16
0.10
0.12
—
—
—
—
0.09
0.09
0.12
0.09
—
0.09
—
∗Molar ratio.
∗∗Yields.
∗∗∗Inherent viscosity, in CHCl3 at 25 ◦C (c = 0.3 g/dL).
poly(carbonate) was obtained only at a 3:1 NaOH/phenol ratio, which
showed the relative effectivity of the transfer process, when the cata-
lysts were used.
For the poly(thiocarbonate) Ib the best results were obtained at
a 3:1 NaOH:phenol ratio. A stoichiometric amount of NaOH the
poly(thiocarbonate) was not obtained without a catalyst, but when the
catalysts were used, very low yields and ηinh values were obtained.
When the NaOH concentration was increased, TBAB and ALIQUAT
336 were effective, and an increase of the yields and ηinh values was
observed principally due to a salting-out effect of the diphenolate to the
organic phase in which the reaction takes place. The same occurs with-
out catalyst but the values were lower. But if the NaOH concentration

246
L. H. Tagle et al.
is increased to twice the stoichiometric, it is possible to see lower val-
ues of both parameters, due to a hydrolysis of the thiophosgene and
the polymeric chains promoted by these lypophilic catalysts, although
TBAB, according to its symmetrical structure, has been described as
effective for analogous synthesis.14 BTEAC was ineffective at all the
NaOH concentration according to its hydrophilic nature.
Table I shows the results obtained for the poly(carbonate)
IIa and poly(thiocarbonate) IIb derived from the diphenol bis(4-
hydroxyphenyl)-ethylmethylsilane. In general for the poly(carbonate)
IIa, the best results were obtained at a 3:1 NaOH:phenol ratio, a
50% in excess respect to the stoichiometric, showing a salting-out ef-
fect of the diphenolate. But if this concentration was increased, the
poly(carbonate) was not obtained or it was possible to see a decrease
of both parameters due to hydrolytic effects. BTEAC was effective at
stoichiometric NaOH concentration, but the effectivity decreased at a
higher concentration. TBAB and ALIQUAT 336, which are more ly-
pophilic catalysts, can promote hydrolytic effects in the phosgene or in
the polymeric chains, resulting in a decrease in the yields in the first
case and a decrease in the ηinh in the second case.
For the poly(thiocarbonate) IIb, an analogous situation was observed
at a stoichiometric concentration of NaOH. When the NaOH concen-
tration is increased, the poly(thiocarbonate) is obtained without a cat-
alyst when TBAB and ALIQUAT 336 are used. But with these cata-
lysts we obtained higher yields. In these cases we cannot suppose a
hydrolytic process because yields and ηinh values are very similar for
the two NaOH concentrations. It is probably that thiophosgene is more
stable toward the hydrolysis than phosgene, which implies obtaining
the poly(thiocarbonate) IIb at twice the required NaOH concentration.
Also, the salting-out effect due to the increase of the NaOH concentra-
tion implies the obtaining of this polymer at this concentration.
Table I shows the yields and the ηinh values obtained for
poly(carbonate) IIIa and poly(thiocarbonate) IIIb derived from
the diphenol bis(4-hydroxyphenyl)-diethylsilane. For both polymers,
only BTEAC was effective as a catalyst, due to its hydrophilic char-
acter suitable for transporting a diphenolate with a higher organic
content such as this. Without a catalyst, polymers practically were not
obtained, which showed the effectivity of the phase transfer process
with BTEAC. Also with BTEAC, it was possible to see a slow decrease
of the yields, probably due to a hydrolytic process. This catalysts of
hydrophilic nature is more effective when the organic content of the
diphenolate increases.
In general, the effectiveness of the phase transfer process was low.
The diphenolates containing Si must show a higher charge dissipation

Poly(carbonates) and Poly(thiocarbonates)
247
due to the stringer electron acceptor character of the Si atom, which is at
least, relative to the carbon analog. Consequently, the best results were
obtained at a 3:1 NaOH:phenol ratio. This effect also was described in
analogous polymers but with Ge as a central atom.6
On the other hand, although the increase of the NaOH concen-
tration displaces the equilibrium to the diphenolate formation, the
higher concentration (4:1 NaOH:diphenol ratio) promotes the hy-
drolytic process of both the phosgene or thiophosgene, and the poly-
meric chains if the OH− anions are transferred to the organic phase
with lipophilic catalysts, with the results being poor in general at
this NaOH concentration. These results are responsible for the low
values of inherent viscosity because this species is of oligomeric
nature.
Also, it is possible to see that when the organic groups that are bonded
to the Si atom are increased, the results turn poorer, which also was
observed in analogous polymers with Ge as the central atom.6 This
effect must be investigated more.
CONCLUSIONS
We can conclude that the phase transfer process was relatively poor
in the synthesis of poly(carbonates) and poly(thiocarbonates) derived
from diphenols containing Si as a central atom. The increase of the
NaOH concentration has influence in the results, in the sense that
it displaces the phenol-phenolate equilibrium, but also increases the
possibility of hydrolysis of the phosgene or thiophosgene and the poly-
meric chains, diminishing the yields in the first case and the ηinh in
the second case. Also it would be necessary in the future to study
further the effect of the increase of the organic groups bonded to the
heteroatom.
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