Biradical Initiation in Photoinitiated Copolymerization of Styrene and Maleic Anhydride

Abstract Poly(styrene‐ co ‐maleic anhydride) (SMAnh) is a copolymer system that is well known for its alternating tendency, which has been thoroughly investigated by many research groups over the decades and is widely used in industry. Investigations have focused almost entirely on thermally initiated systems. However, very few investigations have been conducted on light‐initiated radical copolymerization. In this study, the photoinitiated copolymerization of styrene and maleic anhydride is investigated without the use of an external radical source, such as the classical 2,2‐azobis(2‐methylpropionitrile) (AIBN), benzoyl peroxide (BPO), or any photoinitiators. The initiation of the polymerization is instead found to take place through an excited state biradical generated in situ from a photoexcited charge‐transfer complex (CTC) comprising the donor (styrene) and acceptor (maleic anhydride) monomers. The formation of the complex is found to be solvent dependent. Excitation of the complex results in copolymerization of monomers to afford high‐molecular‐weight (>10 5 g·mol −1 ) alternating copolymers.