Crystalline and liquid crystalline polyesters of phenyl-substituted 4,4'-biphenols and 1,1'-binaphthyl-4,4'-diol .3. Copolymers with 6-hydroxy-2-naphthoic acid

Wholly aromatic, thermotropic copolyesters, derived from either 3-phenyl-4,4'-biphenol, 3,3'-diphenyl-4,4'-biphenol, or 1,1'-binaphthyl-4,4'-diol with either terephthalic acid or 2,6-naphthalenedicarboxylic acid and 30 mol % 6-hydroxy-2-naphthoic acid, were prepared by melt polycondensation reactions and characterized for their thermotropic liquid crystalline properties by a wide variety of experimental techniques. The three copolyesters containing phenyl-substituted 4,4'-biphenols had either lower fusion temperature, T-f, or lower crystal-to-nematic transitions, T-m, than those of an analogous series of copolyesters containing unsubstituted 4,4'-biphenol. Each of them formed a nematic phase above its T-f/T-m values, which was supported from the X-ray diffraction pattern obtained from each of the oriented fibers. Their nematic phases showed both a marbled texture and a Schlieren texture. In one case, a banded texture was also observed, without being subjected to shear. Although the polarized light microscopy study of the fourth copolymer containing 1,1'-binaphthyl-4,4'-diol suggested its nematic phase above its T-f value, X-ray diffraction pattern obtained from its oriented fiber indicated its localized sanidic or boardlike microstructure. No development of crystallinity occurred in each of these copolymers on annealing, which suggested that all of them had random microstructures in their polymer chains. Despite little to no crystallinity in these copolymers, they were not soluble in common organic solvents. As expected, each of them had a broad range of nematic liquid crystalline phase because of the copolymerization effect of the added monomer. They had higher glass transition temperatures, T-g, in the range of 128-180 degrees C than those of other liquid crystalline copolyesters. They exhibited high thermal stability, T-d, in the range of 417-494 degrees C suggesting their convenient melt processing in the nematic liquid crystalline phase at elevated temperatures.