Self-cleaning, transparent, and anti-icing properties of polylactic acid films with stiffness-toughness balance via a stretching-nonsolvent-induced phase separation-liquid infusion process.

Polylactic acid (PLA) is a highly sustainable and fully biodegradable polymer that is regarded as a promising alternative to conventional polyolefin films in packaging applications. Nevertheless, PLA inherently suffers from various bottlenecks such as brittleness and hydrophilicity due to its ester-rich backbone, which lead to its relatively narrow application area. Exploring its promising comprehensive performance should be valuable for the expansion of its applications. In this study, we develop a facile and green strategy of stretching-nonsolvent-induced phase separation-liquid infusion (NIPS-liquid infusion) to fabricate PLA films integrating self-cleaning, high transparency, anti-icing, and stiffness-toughness balance. The NIPS process generates a film surface with a porous crystalline morphology, considerably improving its surface roughness and hydrophobicity. Subsequently, a hydrophobic liquid with refractive index that matches with that of PLA is injected, which not only restores the transparency of the film (with a light transmittance of 90.9%) but also achieves outstanding lubricity and self-cleaning properties. The resulting material maintains its self-cleaning capability and optical clarity under low-temperature conditions without significant loss of stiffness-toughness balance induced by the stretching-induced orientation of the amorphous phase. This work offers a practical route for designing multi-functional PLA-based packaging materials such as for the appliances used in refrigerators.