Diphenylphenacyl sulfonium salt as dual photoinitiator for free radical and cationic polymerizations

Diphenylphenacylsulfonium tetrafluoroborate (DPPS+BF4-) salt possessing both phenacyl and sulfonium structural units was synthesized and characterized. DPPS+BF4- absorbs light at relatively higher wavelengths. The direct and sensitized initiation activity of the salt in both cationic and free radical photopolymerizations was investigated and compared with that of its analogue triphenylsulfonium tetrafluoroborate (TPS+BF4-). Differential scanning photocalorimetry and conventional gravimetric studies revealed that DPPS+BF4- showed higher efficiency for direct and sensitized photopolymerizations of most of the monomers investigated. Although, principally both homolytic and/or heterolytic cleavage is possible, theoretical studies suggested that homolytic pathway is more favored for the generation of reactive initiating species. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 451-457