Cationic polymerization initiated by onium ions

Abstract

4-Chlorobenzene-diazonium, CBD +, N-ethoxyisoquinolinium, EIQ +, and N-ethoxy-4-cyanopyridinium, ECP +, ions, in the form of hexafluorophosphate salts, readily initiate in a dark reaction the cationic polymerization of n-butyl vinyl ether, NBVE, isobutyl vinyl ether, IBVE, and N-vinylcarbazole, NVC, in air-saturated dichloromethane solution at room temperature. Hexafluoro-phosphates of diphenyliodonium, Ph 2I +, triphenylsulphonium, Ph 3S +, N-ethoxy-2-methylpyridinium, EMP +, and N-ethoxy-4-phenylpyridinium, EPP +, ions are much less active. They do not initiate the polymerization spontaneously, but cause a very slow conversion of these monomers into polymers. All onium salts examined in this work are quite unreactive in initiating the polymerization of cyclohexane oxide, CHO, and α-methylstyrene, αMSt. However, the polymerization of aerated CHO containing dissolved EIQ +PF 6 − or CBD +PF 6 − is readily initiated upon the addition of vinyl ether (IBVE) or N-vinylcarbazole. This result indicates that cationic species generated by the reaction of EIQ + or CBD + ions with IBVE or NVC are capable of initiating the polymerization of CHO, which itself is unreactive towards the onium ions under investigation.