Block Copolymers by Using Combined Controlled Radical and Radical Promoted Cationic Polymerization Methods

Summary

A novel synthetic procedure for the preparation of block copolymers based on the combination of diphenylethene (DPE) mediated controlled radical polymerization and radical promoted cationic polymerization is described. In the first step, the controlled polymerization of styrene (St) and methyl methacrylate (MMA) in presence of DPE yields polymers with various structures of diphenylethyl units in the main chain. Upon heating these prepolymers undergo scission to give polymeric radicals. Oxidation of these radicals by onium salts such as diphenyliodonium heaxfluorophosphate (Ph₂I⁺PF₆ ⁻) and N-ethoxy-2-methylpyridinium hexafluorophosphate (EMP⁺PF₆ ⁻) yields reactive cations capable of initiating cationic polymerization of cyclohexene oxide (CHO). Block copolymer structure was confirmed by IR and NMR spectral measurements and GPC analysis.