Chemistry Reference
In-Depth Information
carbonate precursor. A polymer prepared in this way had an intrinsic viscosity (in
CHCl
3
at 25
C) of 0.87 dL/g, a 45:55 head-to-head:head-to-tail microstructure, and
a glass temperature of 173-174
C [281].
Blends of polypropylene short fibres and a pulp of poly(4,4
0
-dioxydiphenyl-2,2-
propane carbonate) or 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane-bis(4-hydroxy-
phenyl)propane-phosgene copolymer have been used to prepare paper substitutes
useful as insulators for high-voltage cables [282].
Modified polycarbonates, proposed as protective coatings for glass, and the effect
of modifying additives on the properties of polycarbonates, have been discussed
[283]. In preparing polycarbonates from 1,1-bis(4-hydroxyphenyl)cyclohexane and
phosgene, partial substitution of phosgene by (ClCOCH
2
SiMe
2
)
2
O or (ClCO
CH
2
CH
2
OCH
2
SiMe
2
)
2
O led to copolymers having improved water- and alkali-
resistance and good adhesion to glass.
Azidoformates have also been applied to polymeric substrates. Polymeric and
non-polymeric compounds, p-RC
6
H
4
NEt(CH
2
)
2
OCON
3
, useful as azo dyes or oil-,
laundry-, and waterproofing agents for polyamide and polyester fibres, have been
manufactured by treatment of a variety of chloroformates (prepared in situ with
phosgene) with sodium azide [284].
Polycarbonates bearing imido terminal groups have been prepared by treat-
ing a mixture of dihydroxy-terminated compounds with phosgene and a chain-
terminating agent containing a substituted imido group. Thus, phosgene was
added to a mixture of p-maleimidobenzoic acid, pyridine, and dichloromethane,
2,2-bis(4-hydroxyphenyl)propane was then added, and the mixture was stirred.
Additional phosgene was added, followed by 6 n hydrochloric acid, to give the
imido-terminated polycarbonate [285].
The effect of tertiary amines and quaternary ammonium salts on the inter-
facial polycondensation of 2,2-di-(4-hydroxyphenyl)propane and phosgene has been
studied [286]. The rate of polymerization of (4-HOC
6
H
4
)
2
CMe
2
with phosgene
in alkali solution is accelerated by the addition of Et
3
N, PhNEt
2
, PhN(CH
2
Ph)
2
,
PhCH
2
NEt
3
Cl, or triethyloctadecylammonium chloride. These compounds not
only act as surface-active agents promoting polymerization at the interface between
the aqueous alkali and organic phases, but also form solution salts, which react
further with the growing polycarbonate in the aqueous phase away from the inter-
face. Addition of these compounds increases the molecular weight of the poly-
carbonates.
Cyclic carbonic acid derivatives, useful as copolymerization components for the
preparation of polycarbonates, are obtained by treating a polyol such as a trime-
thylolalkane (e.g. trimethylolpropane) with a carbonic acid derivative such as a
dialkyl carbonate (e.g. diethyl carbonate). They can be copolymerized with other
organic carbonates at 150-240
C and 0.001-10 mbar to give insoluble, cross-
linked polycarbonates, which can be depolymerized at 240-320
C and 0.001-
2 mbar [287].
The polymerization of trimethylene carbonate (1,3-dioxan-2-one) with complex-
ation catalysts has been discussed [288]. The bulk polymerization of trimethylene
carbonate was conducted at 90, 120, and 150
C in the presence of initiators. In
