Pulse radiolysis and theoretical investigation on the initial mechanism of the e-beam polymerization of epoxy resins. The results obtained on (phenoxymethyl)oxirane

The radical cation of (phenoxymethyl)oxirane (PGE? +) is generated by pulse radiolysis in dichloromethane solution and by direct action of radiation on the title compound. In the pure system its UV-vis spectrum is characterized by two bands at 340 and 430 nm, such that the electronic structure corresponds to a dipole bearing the positive charge on the phenoxy side. At the same time, the phenoxy-oxirane bridge is weakened. Then, the radical cation fragments into a phenoxonium ion and an oxyranylmethyl radical (kPGE - fragm = 1.16 × 107 s- 1). The latter immediately rearranges to an allyloxyl radical by ring opening. It is then conceived that the action of onium salts, as radiation curing initiators of phenoxy-oxirane derivatives, occurs after epoxy ring opening.