Ultrahigh-performance electrospun polylactide membranes with excellent oil/water separation ability via interfacial stereocomplex crystallization

Abstract

Stereocomplex (sc) crystallization between poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) exhibits great potential for the development of high-performance polylactide (PLA) materials because sc crystallites possess many superior physicomechanical properties compared to homo-crystallites. However, it remains a challenge to fabricate electrospun sc-PLA membranes with sufficient mechanical strength and structural integrity for practical applications due to the weak adhesion between fibers. Herein, we devise a new low-temperature sintering mechanism that leads to substantially improved inter-fiber adhesion and the resultant membrane performance. We find that sintering below the melting temperature of sc crystallites can induce the interdiffusion of PLLA/PDLA chain segments from adjacent sc-PLA fibers across the intersections, which subsequently co-crystallize into new sc crystallites capable of tightly welding these fibers together. As a result, the tensile strength and Young's modulus of the electrospun membranes are significantly enhanced from 0.9 MPa and 23.7 MPa to 11.1 MPa and 546.2 MPa, respectively. Critically, the mechanical enhancement is achieved without changing the original porous structure of the electrospun membranes, which is distinctly different from the destroyed membrane structure obtained by conventional thermal annealing at a temperature near the melting temperature of sc crystallites. We further demonstrate that the sintered membranes have excellent chloroform/water separation ability without being destroyed or even swollen. Our overall findings suggest a highly effective approach to fabricate PLA nanofibrous membranes with superior mechanical strength and unprecedented separation performance through interfacial stereocomplex crystallization.