The molecular weight dependence of the crystallization behavior of four-arm poly(L-lactide)

The molecular weight dependence of the crystallization behavior of four-arm poly(L-lactide) (4A-PLLA) was investigated thoroughly by testing the synthesized 4A-PLLA on a differential scanning calorimetry (DSC). The four-arm structure and high molecular weight of resulted 4A-PLLA was first confirmed by 1H-NMR with the evidence from GPC curves. A powerful ability of 4A-PLLA to crystallize in a non-isothermal process was proven. By iso-thermal study, 4A-PLLA displayed a similar approach with the nucleation theory during crystallization when Mn of 4A-PLLA exceeding 5 × 104 g/mol. Half crystallization time (t1/2) and melting temperature of 4A-PLLA showed unusual dependence on the molecular weight, which was attributed to different equilibrium state of molecule chains induced by the different arm length for various samples by excluding the possibility of crystallization regime difference.