Cationic ring-opening polymerization of N-phenylazetidine

The cationic ring-opening polymerization of N-phenylazetidine (NPA) has bee n studied either with methyl trifluoromethanesulfonate or alpha-benzyloxy-o mega-(N-phenylazetidinium) poly(tetrahydrofuran), poly(THF), (1) as an init iator (5 mol-%). A nearly complete polymerization: took place even at 10 de grees C to produce poly(NPA) and poly(THF)-block-poly(NPA) copolymer, respe ctively. Kinetic measurements of the homopolymerization process as well as GPC measurements of the block-copolymer products from 1 have indicated a co ncurrent termination reaction during the polymerization through the intermo lecular nucleophilic attack of N-phenylamino groups along the produced poly (NPA) segment toward a propagating azetidinium group, producing branched po lyamine segments particularly during the prolonged reaction. Thermo-dynamic parameters of the polymerization, i. e., enthalpies and entropies of activ ation for the propagation and for the and entropies of activation for the p ropagation and for th termination, were determined to be Delta H-p(double d agger) = 68 kJ mol(-1), Delta H-t(double dagger) 46 kJ mol(-1), Delta S-p(d ouble dagger) = 68 J mol(-1) K-1, and Delta S-t(double dagger) = 169 J mol( -1) K-1, respectively.