Photocross-Linkable Polymers

Several processes of photocross-linking of polymers are based on the photodimerization of unsaturated groups and on the photodissociation of light labile groups, such as azides. In the present paper we will consider three different methods of cross-linking:

1. Photoinitiation of free radical polymerization of unsaturated side groups attached to a polymer molecule in the presence of a suitable photoinitiator, such as benzoin alkyl ether.

2. Photoinitiation of cationic polymerization of oxirane side groups in the presence of photolabile amine salts, such as diazonium salts, giving rise to the formation of Lewis acid.

3. Electron donor/acceptor complexation of side groups which on photoexcitation exchange an hydrogen atom; this results in cross-linking by free radical combination.