Facile preparation of highly crystalline poly(L-lactide) films with inversed wettability and their potential application in oil-water separation

Highly crystallized poly(L-lactide) (PLLA) films with enhanced hydrophobicity are easily prepared by casting PLLA solution into a poor solvent like isopropyl alcohol (IPA). The crystallinity of the PLLA film can be controlled by PLLA's concentration, the kind of poor solvent, and the volume ratio of poor solvent dichloromethane (DCM). Results show the addition of poor solvents obviously accelerate the crystallization of PLLA film and enhance the crystallinity up to 48.7%. A lower volume ratio of IPA/DCM at higher PLLA concentration as well as a higher volume ratio of IPA/DCM at lower PLLA concentration is conducive to raising the crystallinity of the PLLA film. In the meanwhile, microscopy observation and wettability tests confirm the PLLA films present multidimensional microstructure including fibrils, lamellas, and flower-like stacks or spherulite-like superstructure, and display high porosity as well as enhanced hydrophobicity. Despite the volume ratio of IPA/DCM, the PLLA films prepared at lower concentrations display higher crystallinity, porosity as well as hydrophobicity than those prepared at higher concentrations. The highly crystalline PLLA films with enhanced porosity and hydrophobicity are supposed to be applied in oil-water separation, and so forth.