Poly(phenylenevinylene)s as Sensitizers for Visible Light Induced Cationic Polymerization

Abstract

A novel visible light sensitive photoinitiating system for the cationic polymerization of oxiranes such as cyclohexene oxide (CHO) and vinly monomers such as isobutyl vinylether (IBVE) and N-vinyl carbazole (NVC) using poly(phenylenevinylene) (PPV) derivatives as photosensitizers is described. The cationic polymerization of these monomers was initiated at room temperature upon irradiation in the visible region (λinc > 400 nm) in bulk or methylene chloride solutions with poly(phenylenevinylene)-g-polystyrene (PPV-g-PSt) or poly(phenylenevinylene)-g-poly(e-caprolactone) (PPV-g-PCL), in the presence of oxidizing salts such as diphenyliodonium hexafluorophosphate (DPI), and N-ethoxy-2-methylpyridinium (EMP). The initiation mechanism, based on the optical absorption measurements, free energy changes (ΔG), and proton scavenging studies, involves formation of exciplex by the absorption of light in the first step. Subsequently, an electron transfer from the excited PPV-g-PSt or PPV-g-PCL to oxidizing salt occurs ...