Structural Evolution of Polyglycolide and Poly(glycolide-co-lactide) Fibers during In Vitro Degradation with Different Heat-Setting Temperatures

[Image: see text] The structural evolution of polyglycolide (PGA) and poly(glycolide-co-lactide) (P(GA-co-LA)) with 8% LA content fibers with different heat-setting temperatures was investigated during in vitro degradation using WAXD, SAXS, and mechanical property tests. It was found that the PGA fiber was more susceptible to the degradation process than the P(GA-co-LA) fiber and a higher heat-setting temperature reduced the degradation rate of the two samples. The weight and mechanical properties of the samples showed a gradual decrease during degradation. We proposed that the degradation of PGA and P(GA-co-LA) fibers proceeded in four stages. A continuous increase in crystallinity during the early stage of degradation and a gradual decline during the later period indicated that preferential hydrolytic degradation occurred in the amorphous regions, followed by a further degradation in the crystalline regions. The cleavage-induced crystallization occurred during the later stage of degradation, contributing to an appreciable decrease in the long period and lamellar thickness of both PGA and P(GA-co-LA) samples. The introduction of LA units into the PGA skeleton reduced the difference in the degradation rate between the crystalline and amorphous regions, and they were simultaneously degraded in the early stage of degradation, leading to a degradation mechanism different from that of the PGA fiber.