Synthesis of block copolymers by transformation of photosensitized cationic polymerization to stable free radical polymerization

Anthracene-photosensitized cationic polymerization of cyclohexene oxide at λ = 350 nm in conjunction with onium salts, namely N-ethoxy-2-methyl pyridinium hexafluorophosphate (EMP⁺PF₆ ^-) or diphenyliodonium hexafluorophosphate (Ph₂I⁺PF₆ ^-), in the presence of a stable radical, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), yielded polymers with alkoxyamine terminal groups. These polymers were found to be efficient initiators for stable free radical polymerization (SFRP) of styrene. IR, ¹H-NMR spectral analysis and GPC studies of the obtained polymers show that block copolymers are readily formed as a result of combination of photosensitized cationic and stable free radical polymerization mechanisms.