Morphology, Molecular Mass Changes, and Degradation Mechanism of Poly-L-Lactide in Phosphate-Buffered Solution

The hydrolytic degradation of poly-L-lactide (PLLA) material was investigated in order to elucidate the effects of degradation on the morphology and molecular mass changes. The degradation mechanism and kinetics of PLLA were also studied. Molecular mass decreases and molecular weight distribution becomes broader continuously with an increase in the degradation time. After 20 weeks of degradation, there were a large number of diagonal striations on the surface and many erosive holes in the interior of the PLLA materials. The degradation mechanism of PLLA is indicative of an autocatalysis process and simple bulk hydrolysis at the same time, and the terminal hydroxyl group of the oligomer plays an important role. The degradation of PLLA complies with first-order kinetics, and the rate constant of the biodegradation process of PLLA is 9.2 × 10−3 day−1.