Primary processes of the radiation-induced cationic polymerization of aromatic olefins studied by pulse radiolysis

Abstract By pulse radiolysis of solutions of aromatic olefins (styrene, 1-methylstyrene, 1,1-diphenylethylene) in non-polar solvents (cyclohexane, carbon tetrachloride, n -butylchloride) the mechanism and kinetics of primary processes of radiation-induced cationic polymerization were investigated. In cyclohexane, radical cations of the olefins are generated by charge transfer from solvent cations ( k about 10 11 dm 3 mol -1 s 1 ). These cations dimerize in a diffusion-controlled reaction ( k ≈ 10 10 dm 3 mol -1 s 1 ). The next step of chain-growth is slower by 3 to 4 orders of magnitude. In carbon tetrachloride and in n -butyl chloride growing olefin cations are produced by a reaction of radical cations with solvent as well as by addition of solvent carbonium ions to the monomer. In strongly acidic aqueous solution of olefins radical cations produced indirectly from hydroxycyclo-hexadienyl radicals dimerize and react in a subsequent step by deprotonation forming non-saturated dimer radicals. The reaction mechanism established that in the case of radiation-induceders of magnitude. In cationic polymerization it is not possible to define a uniform first step of the chain reaction.