Novel photoacid generators for cationic photopolymerization
Cationic photopolymerization is a powerful method for UV-curing of epoxy, vinyl ether and oxetane monomers. Little attention has been paid to it over the last few decades compared to the corresponding free radical applications due to unsuitable and inefficient photo-acid generators (PAGs) used for photoinitiation. We introduce a novel type of PAG based on the tetrakis(perfluoro-t-butyloxy)aluminate anion. In facile preparations, diphenyliodonium and triarylsulfonium salts were synthesized, followed by characterization of absorbance and thermal stability. Comparative photo-differential scanning calorimetry (photo-DSC) studies with common onium salt PAGs showed the advantageous reactivity of the novel alkoxyaluminate-based cationic photoinitiators. The novel diphenyliodonium PAG was also examined in photosensitization studies for potential use in higher wavelength applications.