Superhydrophobic and self-cleaning PLA/TPU foams via interfacial design and supercritical CO2 foaming

Porous polymer foams with engineered surface structures are of great interest for superhydrophobic and self-cleaning applications. However, most existing surface modification techniques rely on complex processing routes and provide limited control over surface porosity and morphology. In this work, we propose a simple and sustainable strategy that integrates interfacial design with supercritical carbon dioxide (scCO 2 ) foaming. Bilayers of poly(lactic acid) (PLA) and PLA/thermoplastic polyurethane (TPU) were constructed, in which dispersed TPU domains acted as heterogeneous nucleation sites, thereby facilitating the formation of porous surfaces. The morphology and wettability of the foams were further tailored through TPU content, hot-pressing temperature, and foaming conditions. Subsequent modification with fluorinated silica nanoparticles imparted robust superhydrophobicity (water contact angle >150°, sliding angle <5°) and durable self-cleaning ability even after repeated contamination. This environmentally friendly method thus provides a scalable route to multifunctional foams and highlights the potential of interfacial design for sustainable polymer materials.