Photoinitiated cationic polymerization by dialkyl-4-hydroxyphenylsulfonium salts

On irradiation with ultraviolet light, dialkyl-4-hydroxyphenylsulfonium salts undergo reversible photodissociation and in the process generate ylids and Brønsted acids. When the anions are nonnucleophilic in character, as, for example, BF₄^?, AsF₆^?, PF₆^?, and SbF₆^?, the strong acid which is produced is capable of initiating cationic polymerization. The polymerization of several monomers was carried out to demonstrate the general applicability of these new photoinitiators.