Chemistry Reference
In-Depth Information
High molecular weight polycarbonates are prepared without using phosgene by
melt polycondensation of dihydric phenols with carbonic acid diesters using car-
boxylic acids (e.g. phenylacetic acid) and electron-donating amines (e.g. 2-methyl-
imidazole) as catalysts [293].
Starting from 2,2
0
,6,6
0
-tetrabromobisphenol A and/or 2,2
0
,6,6
0
-tetrachlorobi-
sphenol A, heat- and light-resistant aromatic poly(ester carbonate)s have been
prepared with the acid chloride of terephthalic or the diphenyl ester of 2,5-
dichloroterephthalic acid and diphenyl carbonate (DPhC)orphosgene [294].
Poly(ester carbonate)s with low birefringences and small photoelastic coe
cients
have been prepared by mixing a solution of 1,1-bis(3-methyl-4-hydroxyphenyl)-
cyclohexane in 2 n aq. NaOH and a solution of phthaloyl dichloride in dichloro-
methane, adding a solution of an phosgene oligomer in dichloromethane and 7%
aqueous triethylamine, allowing the mixture to react for 5 min, adding additional
oligomer solution and PTBP, reacting for a further 40 min, and quenching with
phenyl chloroformate [295].
Polycarbonates and polythiocarbonates from phosgene and thiophosgene, respec-
tively, have been prepared from diphenols with chlorinated aromatic side groups
under phase-transfer conditions using several quaternary ammonium and phos-
phonium salts and dichloromethane as solvent. The effect of varying the catalyst
and of the structure of the diphenol was studied [296].
Phosgene equivalents and their substitutes have found many applications in the
synthesis of polycarbonates. Table 5.4 lists some examples employing triphosgene.
Tab. 5.4.
Polycarbonates from triphosgene and dihydroxylic compounds [297].
Dihydroxylic Compound
Reaction Conditions
Polymer
Refs.
triphosgene/CH
2
Cl
2
;
1 n NaOH
Thermotropic
polycarbonates
298
HO
OH
triphosgene/CH
2
Cl
2
;
1 n NaOH
Thermotropic
polycarbonates
298, 299
HO
OH
HO
OH
triphosgene/1 n
NaOH/CH
2
Cl
2
Polycarbonate/styrene/
acrylonitrile copolymer
300, 301
CH
3
HO
C
OH
CH
3
triphosgene/
CH
2
Cl
2
/Py
Functionalized
polystyrene
302
HO
CH
C
6
H
5
CH
2
OH
n
Brominated diphenol-
polystyrene
triphosgene/
CH
2
Cl
2
/Py
Block copolymer
303
triphosgene/water/
KOH, reflux
Thermolabile polymer
304
HO
OH
triphosgene/Py/
toluene
Wax-type polymer
305
HO
OH
