Regulating photochemical behavior and property of imidazolium-based water soluble polysiloxane macromolecular photoinitiators by anions

Abstract

Five polysiloxane macromolecular photoinitiators containing different anion structures with ionic liquid character ([Si-di2959Im][X] (X = Br−, Ph4B−, TsO−, NO3−, CF3COO−)) were designed and synthesized. The effect of different anion structures on photochemical behavior, phoinitiating mechanism, the water solubility, thermal property and volatility of the photoinitiators was systematically explored. [Si-di2959Im][X] have high extinction coefficient that reaches up to 40,210 M−1 cm−1, and similar photoinitiating activity and mechanism to 2-hydroxy-1-[4-(2-hydroxyethoxy) phenyl]-2-methylpropan-1-one (Irgacure 2959), while the photopolymerization induction periods of the TPGDA systems initiated by [Si-di2959Im][X] (X = Ph4B−, CF3COO- and NO3) are slightly shorter than that by Irgacure 2959. In addition, [Si-di2959Im][X] have not only good water solubility, but also desirable thermal property and low saturated vapor pressure. The order of water-solubility of [Si-di2959Im][X] is Ph4B− <Br− <TsO− <NO3− <CF3COO−, the order of the saturated vapor pressure is CF3COO− < Ph4B−< NO3−< Br− < TsO−. High-performance liquid chromatography chromatograms reveal that the migration of the photolysis fragments of [Si-di2959Im][X] from the cured material is mitigated significantly by their high molecular weights.