Side-Chain LC Block Copolymers with Well Defined Structures Prepared by Living Anionic Polymerization. 2: Effect of the Glass Transition Temperature of Amorphous Segments on the Phase Behaviour and Structure of the LC Segment

Abstract

We have prepared two classes of LC diblock copolymers, OcSt-b-LC and MeStb-LC, by living anionic polymerization. These are composed of the side-chain LC polymer as one segment and two different amorphous polymers, poly(octyl styrene) (OcSt) and poly(α-methyl styrene) (MeSt), as the other segment. OcSt and MeSt segments have glass transition temperatures of ⁻60 °C and 160 °C respectively, which are relatively lower and higher than the transition temperatures of crystal–S_A (∼90 °C) and S^A–isotropic (∼130 °C) in the LC segment. In OcSt-b-LC the lamellar domain size decreases gradually from that of the crystal phase to that of the isotropic phase, indicating that the global conformation of the backbone changes throughout the S^A temperature region. In MeSt-b-LC, in contrast, no change in the lamellar size is observed and the crystallinity of the LC segment is reduced in comparison with that in OcSt-b-LC while the liquid crystal is well formed. Such a distinction between two copolymer systems, arising from an interplay between the LC and amorphous segments, shows that the global conformation of the backbone is significant for understanding the phase behaviour and structure of side-chain LC polymers.