Synthesis of side-chain liquid crystalline homopolymers and block copolymers with cyanobiphenyl moieties as the mesogen by living anionic polymerization and their thermotropic phase behavior

We performed the anionic living polymerization of 6-[4-(4'-cyanophenyl)phen oxy]hexyl methacrylate. By a selection of suitable initiations, the cyano g roup was completely stable toward the propagating enolate anion, and the an ionic polymerization proceeded with a living nature. The homopolymers could thus be prepared with a wide range of molecular weights from 6000 to 20 00 0, a narrow molecular weight distribution of less than 1.14, and different tacticities. All the polymers exhibited the smectic A phase in which two me sogenic groups were included within a smectic layer of thickness 36.0 Angst rom. The isotropization temperature of the smectic A phase increased with t he increase of the molecular weight and leveled off at around 15 000. No cr ystallization took place so that the smectic A phase was glassified. Well-c ontrolled block copolymers with methyl methacrylate and styrene were also p repared by living anionic polymerization, and their thermotropic phase beha vior and structures are described in a relation to a microphase separation of the two different segments.