Synthesis and self-assembly of diblock copolymers bearing 2-nitrobenzyl photocleavable side groups

The light-responsive behavior in solution and in thin films of block copolymers bearing 2-nitrobenzyl photocleavable esters as side groups is discussed in this article. The polymers were synthesized by grafting 2-nitrobenzyl moieties onto poly(acrylic acid)-block-polystyrene (PAA-b-PS) precursor polymers, leading to poly(2-nitrobenzyl acrylate-random-acrylic acid)-block-polystyrene (P(NBA-r-AA)-b-PS) block copolymers. The UV irradiation of the block copolymers in a selective solvent for PS led to the formation of micelles that were used to trap hydrophilic molecules inside their core (light-induced encapsulation). In addition, thin films consisting of light-responsive P(NBA-r-AA) cylinders surrounded by a PS matrix were achieved by the self-assembly of P(NBA-r-AA)-b-PS copolymers onto silicon substrates. Exposing these films to UV irradiation generates nanostructured materials containing carboxylic acids inside the cylindrical nanodomains. The availability of these chemical functions was demonstrated by reacting them with a functional fluorescent dye. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 599-608, 2012