Two routes towards photoinitiator-free photopolymerization in miniemulsion: Acrylate self-initiation and photoactive surfactant

摘要

Two novel photoinitiator-free approaches to photopolymerize acrylic monomers with a conventional Hg lamp starting from an acrylates monomer miniemulsion are investigated. In one system the acrylate nanodroplet reaction is self-initiated and in the other the use of a photoactive diphenyl ether surfactant yields phenyl and phenoxyl initiating radicals upon UV irradiation. Photopolymerization kinetics are monitored in situ by real-time Fourier transform near infrared spectroscopy (RT-FTNIR) and the colloidal properties are systematically investigated by dynamic light scattering (DLS). The up-scaling of these PI-free miniemulsion photopolymerizations is carried out in an annular photoreactor. Acrylate miniemulsion polymerization is conducted under UV-C irradiation without the assistance of any radical photoinitiator. The uses of monomer self-initiation and a photoINISURF as two separate routes to yield polymer latexes are investigated and both achieve 100% conversion. The former route also gives full conversion when it is scaled up to a 400 mL photoreactor.