Synthesis of block copolymer with photo-decomposable polyurethane and its photo-initiated domino decomposition

A block copolymer consisting of a photo-decomposable polyurethane and poly(methyl methacrylate) (PMMA) was developed. The end-functionalized polyurethane (P2) was synthesized by polycondensation with the end-functionalization reagents. P2 possesses the photosensitive o-nitrobenzyl group and the 2-bromoisobutyryl group as the initiator of the atom transfer radical polymerization (ATRP). The block copolymer (P2-b-PMMA) was synthesized by the ATRP of methyl methacrylate (MMA) with P2 as the macroinitiator. The P2 block in P2-b-PMMA was decomposed by photo-irradiation at 365 nm by the initiation of the photo-fries rearrangement of the urethane linkage and the subsequent domino reaction consistent with the elimination of the aza-quinone methide and decarboxylation. The photo-initiated decomposition of the P2 segment in the thin-film state was accomplished.