Abstract:In this work, a series of novel metal-free anionic polymerization systems, which are composed of onium salts (including some kinds of quaternary ammonium and phosphonium halides) as initiators in combination with alkyl borane as catalyst, were developed for the first time. These systems present excellent polymerization activity and inhibition on side reactions, especially chain transfer reactions. Polypropylene oxides (PPO) with well controlled molecular weights and distributions were successfully synthesized. The chemical shift changes of PO characterized by 1H-NMR spectra clearly confirm the activation of alkyl borane to monomer PO, which has a great relationship with the amounts of borane catalyst. Meanwhile, the effects of solvents and the sizes of onium salts on polymerization were also studied to verify the mechanism and process of polymerization. Owing to its notable living polymerization feature, block polyether (PPO-b-PEO) with definite structures can be easily fabricated through the sequential polymerization of propylene oxide (PO) and ethylene oxide (EO).