Synergistic Effect of Multi-Arm Architecture and Molecular Weight on Crystallization and Degradation Behavior of Star-Shaped Poly(Lactic Acid)

Star-shaped poly(lactic acid)s (PLAs) with two to five arms were synthesized by ring opening polymerization using tin(II) 2-ethylhexanoate as catalyst and polyols as initiators. The effects of molecular weight together with multi-arm architecture on crystallization behavior, spherulite morphology and alkaline degradation behavior of star-shaped PLAs have been investigated. The results indicate that the multi-arm architecture interfered with spherulite growth, but promoted nucleation and alkaline degradation of star-shaped PLAs. Interestingly, with the increase of molecular weight (Mn), the crystallization rate first increased and then decreased, while the alkaline degradation rate was the opposite. The characteristic crystallization and alkaline degradation behavior of star-shaped PLAs were discussed based on the competition between segmental mobility and central core confinement.