Effect of the polymer architecture on the photoinduction of stable chiral organizations

Abstract

The paper presents a series of light responsive block copolymers that have been prepared by sequential polymerization of propargyl methacrylate and methyl methacrylate by atom transfer radical polymerization (ATRP). The pendant alkyne groups of the poly (propargyl methacrylate) block have been subsequently modified with azides from 2,2-bis(hydroxymethyl)propanoic acid decorated with two motifs, either two azobenzenes or one azobenzene and one biphenyl. This general and versatile synthetic approach simplifies the rational inclusion of structural modifications onto these polymers and, thus, establishing structure-properties relationships as a way to tailor the final properties of the material. By polymerizing the poly(propargyl methacrylate) firstly and poly(methyl methacrylate) secondly, block copolymers with low mass fractions, i.e. highly diluted contents, of the photoresponsive block have been achieved where the effect of the polymeric architecture on the induction of chirality using circularly polarized light (CPL) and its temporal stability has been evaluated. The relevance of the liquid crystallinity on the photoinduction of chirality in the block copolymers has also been investigated mainly in relation to thick films of good optical quality.