F. Ignatious et al., LIQUID-CRYSTALLINE BLOCK-COPOLYMERS CONTAINING RIGID UNITS AND FLEXIBLE ETHYLENE TEREPHTHALATE SEGMENTS, Journal of polymer science. Part A, Polymer chemistry, 33(8), 1995, pp. 1329-1340
Liquid crystalline block copolymers containing different compositions
of terephthaloyl bis(4-oxybenzoyl) (triad) mesogen and flexible ethyle
ne terephthalate (ET) units, were synthesized in tetrachloroethane/pyr
idine (TCE/Py) at 150 degrees C and in 1-chloronaphthalene (1-CN) at e
levated temperatures. Inherent viscosities of the PET block copolymers
were always lower than 0.25 dL/g. By replacing the ET blocks with but
ylene terephthalate (BT) blocks, a copolymer of higher inherent viscos
ity (> 0.8 dL/g) was synthesized in 1-CN at 220 degrees C. Formation o
f low molecular weight PET copolymers was attributed to: (1) insolubil
ity of the block copolymer in TCE/Py and (2) formation of side product
s which alter the stoichiometry of the reactants when the reaction was
carried out in 1-CN. The block copolymers were characterized by H-1 a
nd C-13-NMR spectroscopy. Copolymer compositions were calculated from
H-1 and C-13-NMR data. Thermal behavior of these copolymers was analyz
ed by DSC and polarizing optical microscopy. All copolymers exhibited
a nematic liquid crys talline texture. (C) 1995 John Wiley and Sons, I
nc.