Abstract This article describes the photoinitiated cationic copolymerization of 1,6,8,13-tetraoxaspiro [7,7] tridecanes (SOC7), unconstrictive monomer, and 3,4-epoxycyclohexylmethyl 3′,4′-epoxycyclohexane carboxylate (ERL-4221). With four photoinitiators-Bis[4-(diphenylsulfonio) alkyl phenyl] sulfide-Bishexafluoroantimonate (sp-170), Bis[4-(diphenylsulfonio) alkyl phenyl] Sulfide-Bishexafluorophosphite (sp-150), Benzoloxyphenylbenzylmethyl sulfonium hexafluoroantimonate (BBS) and p-hydroxyphenyl benzyl methyl sulfonium hexafluoroantimonate (PHS). The effect of photoinitiator type on the photocuring rate have been discussed. The test results show the sp-170 is the most efficient photoinitiator. The Tg as might be expected is independent of photoinitiator type, but results indicates that Tg increased with the irradiation time.