Preparation of side-chain liquid crystalline Azopolymers by CuAAC postfunctionalization using bifunctional azides: Induction of chirality using circularly polarized light

Abstract

Well-defined side-chain liquid crystal azopolymers have been synthesized by click chemistry of poly(propargyl methacrylate) with bifunctional liquid crystalline azides to produce materials with large degrees of functionalization. A polymeric scaffold having pendant alkyne groups was prepared by atom transfer radical polymerization (ATRP) and postfunctionalized by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) using homo- and heterobifunctional azides. The azides are derivatives of 2,2-bis(hydroxymethyl)propanoic acid (bis-MPA) containing photoresponsive azobenzene and/or liquid crystalline biphenyl moieties. The approach is a convenient alternative to increase the density of functional units in side-chain polymers having moderate polymerization degrees and to modulate the properties of the final material. The article describes the synthesis, characterization, and liquid crystalline properties of the obtained polymers. The effect of the chemical structure and the possible cooperative effects between functional units in the photo-induction of chirality are also evaluated. A switchable photo-transference of chirality from the circularly polarized light (CPL) to material has been achieved. © 2012 Wiley Periodicals, Inc.