Synthesis of Well-Defined Alternating Copolymers by RAFT Copolymerization of N-Vinylnaphthalimide

A novel nonconjugated N-vinyl monomer, N-vinylnaphthalimide (NVNPI), was copolymerized with various comonomers via reversible addition-fragmentation chain transfer process. Two different chain transfer agents (CTAs), O-ethyl-S-(1-ethoxycarbonyl) ethyldithiocarbonate (CTA 1) and benzyl 1-pyrrolecarbodithioate (CTA 2), were compared for these copolymerizations with 2,2'-azobis(isobutyronitrile) as an initiator. The structures of the resulting copolymers were characterized by H-1 and C-13 NMR spectroscopy, suggesting the sufficient incorporation of NVNPI, when methyl acrylate and N-isopropylacrylamide (NIPAAm) were used as comonomers. The copolymerization of NVNPI and NIPAAm using CTA 2 afforded well-defined copolymers with a predominantly alternating structure, controlled molecular weights (M-n = 2000-10700), and low molecular mass distributions (M-w/M-n = 1.21-1.29). Characteristic optical properties of the naphthalimide-containing copolymer were investigated by UV-vis and fluorescence spectroscopic methods.