Melt-crystallization behavior of triarm poly(propylene oxide block L-lactide) (PPO-b-PLLA) copolymer was investigated by means of DSC. Kinetics of melt-crystallization of the samples were investigated in temperature range from 388 to 407 K, and the results were treated with Avirami equation and Arrhenius equation. Based on Lauritzen-Hofmann nucleation and growth theory, the crystallization mechanisms of triarm PPO-b-PLLA copolymer was analyzed, presenting the transition from regime II to regime III with the variation of the chemical structure. And value of Kg(Ⅲ)/Kg(Ⅱ) was in the range of 2.0～2.2, which agrees with the value by LH theory. Both values of fold surface free energy (σe) and chain folding work (q) of the copolymer were much higher than those of PLLA homopolymer, due to the crystallization process of PLLA segments in copolymer hided by bonding PPO segments. And the lower surface nucleation rate occurred in the case of the triarm PPO-b-PLLA copolymer.

Key words: poly(propylene oxide), poly(L-lactide), triarm copolymer, crystallization