Liquid-crystalline main-chain polymers with a poly(p-phenylene terephthalate) backbone. 1. Synthesis, characterization and rheology of polyesters with alkoxy side chains

The influence of the position and length of alkoxy substituents on the phase behavior of poly(p-phenylene terephthalate)s was investigated by differential scanning calorimetry and rheol. measurements. The 2 polymers with dodecyloxy and hexyloxy side chains on the terephthalate moiety (I and II, resp.) both showed stable liq.-cryst. phases. For these 2 polymers the location of the transition temps. as a function of the mol. wt. (inherent viscosity) leveled off above an inherent viscosity of 2dL g-1. Rheol. measurements indicated that the layered mesophase, shown by II and I, behaves more like a solid than a liq. For the nematic mesophase, only shown by II, a min. in the viscosity-temp. curve was found. The polymer with dodecyloxy substituents on the hydroquinone moiety only shows mesomorphic behavior on cooling, while the polymer with dodecyloxy substituents on both Ph rings does not show any liq.-cryst. behavior. [on SciFinder (R)]