Green Chemistry: Sunlight-Induced Cationic Polymerization of Renewable Epoxy Monomers Under Air

The recently developed silyl radical chemistry is used here for the free-radical-promoted cationic polymerization process (FRPCP) of two epoxy monomers (epoxidized soybean oil and limonene dioxide) that are representative of green monomers. The new developed photoinitiating systems are highly efficient under air upon a solar irradiation in autumn French weather and, for example, lead to 60% conversion after 25 mn and form a completely tack-free and uncolored coating after 1 h. Polymerization profiles obtained upon a visible light irradiation delivered by a xenon lamp or a 405 nm diode laser under air show that 70% conversion can be easily achieved after 400 s of exposure. Excited-state processes are investigated and discussed.