Abstract: The primary reaction of iodonium salt/amine combination initiation system was studied. From the experimental results, the following reaction mechanism is proposed. The charge transfer complexes between iodonium salt and amine in the ground state (CTC) and in the excited state (exciplex) occur in the polar solution, and under irradiation, this combination system undergoes electron transfer process to produceamine radical cation and diphenyliodine radical (Ph₂I·), the latter can further cleavage to iodobenzene and phenyl radical (Ph·). These radical and radical cation species formed result in a vinyl polymerization. These reaction processes were proved by means of IR, ¹HNMR, GC-MS spectra and elementary analysis.

Key words: onium salt/amine system, photoinitiation, primary reaction