Cationic Photopolymerization Initiated by a Photocatalytic Complex Sensitive to Visible Light at 520 nm

For the cationic photopolymerization of high value, we designed a new visible-light initiator complex consisting of the visible-light sensitive titanium dioxide (Pyx%:TiO2, x = 3, 6, 9, 12), octanioc acid and iodonium salt (Iod). The ternary complex was proved to efficiently initiate the cationic ring-opening polymerization of the epoxide under the light irradiation at the wavelength of 520 nm. By using gas chromatography-mass spectra (GC-MS), electron spin resonance (ESR) and 1H-nuclear magnetic resonance (1H-NMR), the mechanism studies clearly presented that the Pyx%:TiO2 photocatalyzed the oxidation reaction of octanioc acid in the pathway of photo-Kolbe decarboxylation. Meanwhile, Iod was decomposed by the photocatalytic reduction reaction. The results of this visible-light photocatalytic cationic polymerization process were analyzed by using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and gel permeation chromatography (GPC). The conversion of the epoxide can reach up to 93.8%.