Photocrosslinking of silicones. Part 16. Peculiarity of the sensitized photolysis of lipophilic iodonium salts and their influence on the crosslinking kinetics of vinyl ether derivatives

Abstract

The crosslinking kinetics of vinyl ether derivatives using diphenylanthracene/iodonium salts can be described by means of an ideal crosslinking kinetics. The measured dependence of the reciprocal reaction rate vs. reciprocal iodonium salt concentration shows that interaction between sensitizer and iodonium salt take place. The observed crosslinking kinetics reflects the kinetics of the sensitizer photolysis in typical nonpolar aprotic solvents. Dynamic fluorescence quenching shows that in vinylether derivatives iodonium salts do not quench the fluorescene of DPA. Nevertheless a bleaching of DPA can be observed in the system used. This fact shows that the pathway of the photoinduced electron transfer via the excited singlet state of DPA is neglectable. Such photochemistry was also observed in nonpolar solvents, where the photochemistry of the system is reduced to the photochemistry of the observed CT-complex between sensitizer and iodonium salt. All in all, the crosslinking kinetics of vinylether derivatives by means of DPA/iodonium salts combinations reflects the kinetics of the sensitized iodonium salt photolysis in nonpolar solvents.