Cationic ring-opening polymerization of N-phenylazetidine

The cationic ring-opening polymerization of N-phenylazetidine (NPA) has been studied either with methyl trifluoromethanesulfonate or alpha-benzyloxy-omega-(N-phenylazetidinium) poly(tetrahydrofuran), poly(THF), (1) as an initiator (5 mol-%). A nearly complete polymerization: took place even at 10 degrees C to produce poly(NPA) and poly(THF)-block-poly(NPA) copolymer, respectively. Kinetic measurements of the homopolymerization process as well as GPC measurements of the block-copolymer products from 1 have indicated a concurrent termination reaction during the polymerization through the intermolecular nucleophilic attack of N-phenylamino groups along the produced poly(NPA) segment toward a propagating azetidinium group, producing branched polyamine segments particularly during the prolonged reaction. Thermo-dynamic parameters of the polymerization, i. e., enthalpies and entropies of activation for the propagation and for the and entropies of activation for the propagation and for th termination, were determined to be Delta H-p(double dagger) = 68 kJ mol(-1), Delta H-t(double dagger) 46 kJ mol(-1), Delta S-p(double dagger) = 68 J mol(-1) K-1, and Delta S-t(double dagger) = 169 J mol(-1) K-1, respectively.