Magnetic orientation of microcylinders in liquid crystalline diblock copolymer and clarification of its orientation mechanism

Abstract

The liquid crystal (LC) block copolymers composed of side-chain LC polymer (LCP) and polystyrene (PS) segments with various molecular weights and block contents were prepared by atom transfer radical polymerization, and their microsegregated structures were examined for magnetic alignment. Well-aligned samples have been prepared only for the low molecular weight block copolymers with cylindrical microdomains of PS dispersed in the LCP matrix. The prerequisites for perfect alignment of the microdomain structure are (1) coincidence of the disorder-order transition of the microdomain with the isotropic to nematic transition of the LCP segment, and (2) anchoring of the LC mesogen parallel to the microdomain interface. Well-oriented cylindrical and/or anisotropic microsegregated structures are also observed for the mixtures of a LC homopolymer and a LC block copolymer irrespective of extremely low PS segment content of 12-2%. Such persistent formation of anisotropic PS microdomains in the LC field indicates a significant interplay between the microdomain and liquid crystalline structures. © 2006 The Society of Polymer Science, Japan.