The role of crystallinity on the crazing micromechanism in poly(L-lactic acid) thin film

Poly(l-lactic acid)(PLLA) is a kind of semi-crystalline polymers that could be hydrolyzed through hydrolytic scission of the ester groups. Because of its biocompatibility and biodegradability, it is used widely in medical applications, which degradation and change in mechanical properties during hydrolyzing were the key factors. A.C. Renouf-Glauser et al. had investigated the effect of crystallinity on the deformation mechanism of bulk PLLA, but few studies focused on the mechanism of thin films. In the study we aimed to comprehend how various crystallinities affected the mechanical properties of PLLA and the effect of hydrolysis on PLLA. "String-of-pearls" structures revealed in the pristine and high-crystallinity PLLA, proving external tensile stress would lead to the disentanglement of lamellae. By using a simple calculation we found the diameter of lamellae would domain crazes propagation. In hydrolyzed test we found that the micromechanism of PLLA would be affected.