Photoinitiated cationic polymerization of unconventional monomers namely, benzoxazines, monothiocarbonates and macromonomers of poly(E-caprolactone) and poly(ethylene oxide) is described. Ring opening polymerization of benzoxazines and thiocarbonates by direct and sensitized photoinitiation using onium salts was studied. The structures of the resulting polybenzoxazine were complex and related to the ring opening process of the protanated monomer either at through oxygen or nitrogen atoms. in the case of monothiocarbonate, the polymerization was accompanied with isomerization of thiocarbonate group. The potential use of macromonomers in photoiniated cationic polymerization to design complex macromolecular structures such as graft copolymers, water-borne photoresist materials and networks with dangling chains was presented. Photoinduced oxidative polymerization of thiophene, precursor for conducting polymers, using onium salts was also demonstrated.