Mapping between chain configuration and mechanical properties of poly(L-lactic acid) monofilaments via hydrolysis induction

Abstract

Poly(L-lactic acid) (PLLA), as a substrate material, has been widely utilized in the field of biodegradable vascular stents. Prior to implantation, it is particularly crucial for these devices to assess the relationship of the mechanical properties and microstructures during full degradation cycle. Although previous studies have primarily focused on structural parameters such as crystallinity and molecular weight, there are relatively few reports that explore the impact of microstructure on mechanical performance from the perspective of chain configuration during the degradation. In this study, three types of PLLA monofilaments with short chains (SCs), transitional chains (TCs), long chains (LCs) were prepared via 50 °C hydrolysis. The stress-strain curves of these monofilaments were quantitatively evaluated, focusing on the critical parameters across the elastic, yield, and strain-hardening stages. The results show that throughout the 17- day degradation cycle (equal to 3 months via 37 °C hydrolysis), PLLA monofilaments undergo a transition from LCs to TCs and subsequently to SCs. Simultaneously, the Young's modulus exhibits a continuous increase, while the strain hardening slope demonstrates a decrease. These findings may indicate that SCs primarily enhance the elastic modulus, TCs influence yield stress, and LCs govern strain-hardening behavior. Therefore, elucidating the relationship between chain configuration and mechanical behaviors may provide experimental references to identify the degradation stage of PLLA materials in practical applications.