RIGID ROD POLYMERS WITH FLEXIBLE SIDE-CHAINS - SYNTHESIS, STRUCTURE AND PHASE-BEHAVIOR OF POLY(3-N-ALKYL-4-OXYBENZOATE)S

The synthesis of poly(3-n-alkyl-4-oxybenzoate)s (PAOB-n) with n = 3-18 is reported. The sufficient solubility of these comb-like polymers with stiff-chain backbones allows the determination of the Kuhn length (100-200 angstrom). The unit cells could be determined for PAOB-n with n = 3 and 5. All PAOB-n form thermotropic mesophases. For n = 3 a nematic phase is found. For n = 5 there is a transition from a smectic-like, layered mesophase to a nematic mesophase. PAOB-n with n greater-than-or-equal-to 6 solely form layered mesophases. Except for n = 3, all PAOB-n exhibit a transition to the isotropic state. The transition temperature is lowered monotomically with increasing n.