Rigid rod polymers with flexible side chains: Synthesis, structure and phase behaviour of poly(3- n-alkyl-4-oxybenzoate)s

Abstract

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 Å). 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 ⩾ 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.