SYNTHESIS AND CHARACTERIZATION OF REGIOREGULARLY RING-SUBSTITUTED, LIQUID-CRYSTALLINE AROMATIC POLYESTERS

A series of regioregularly ring-substituted aromatic homopolyesters has been synthesized, and their general properties are compared with those of randomly substituted polymers. The newly synthesized polymers are poly(oxy-1,4-phenyleneoxy-2-bromoterephthaloyl), poly(oxy-1,4-phenyleneoxy-2-nitroterephthaloyl), poly(oxy-2,7-naphthalenediyloxy-2-bromoterephthaloyl), and poly(oxy-2-bromo-1,4-phenyleneoxy-2-bromoterephthaloyl). The polymers were prepared via low-temperature solution polymerization of 4-hydroxyphenyl 2-substituted terephthalates, 2-(7-hydroxynaphthyl) terephthalate, or 2-bromo-4-hydroxyphenyl 2-bromoterephthalate, all of which were prepared via multistep synthetic routes. The polymers of regular microchemical structures have much higher melting temperatures and greater degrees of crystallinity than those of irregularly substituted polymers. The glass transition temperature was also found to be dependent on the manner in which the substituents are located. Positional isomerism of the substituents leads to dissimilar structures of the crystalline regions.