Near-Infrared-Induced Cationic Polymerization Initiated by Using Upconverting Nanoparticles and Titanocene.

A new near-infrared (NIR)-sensitized photoinitiating system for free-radical-promoted cationic polymerization of oxirane and vinyl monomers such as cyclohexene oxide, and n-butyl vinyl ether (BVE), and N-vinyl carbazole (NVC) is described. A three-component photoinitiating system consists of upconverting nanoparticles (UCNPs), titanium-complex free radical photoinitiator (Irgacure 784, titanocene), and diphenyl iodonium hexafluorophosphate (Ph2 I+ PF6 - ). Upon NIR laser irradiation at 980 nm, the radicals generated from titanocene by the visible light emitted by UCNP abstract hydrogen or add to the monomer, forming electron donor radicals that can be oxidized by iodonium salt to initiate cationic polymerization.