Super-hydrophobic poly(L-lactic acid)/TiO₂ nanocomposite membrane with biomimetic microarchitectures for passive...

Developing efficient passive anti-icing surfaces is crucial for mitigating ice-related hazards in industrial sectors. Herein, superhydrophobic poly(L-lactic acid) (PLLA)/TiO₂ nanocomposite membranes, featuring unique biomimetic "straw-bundle-like" microarchitectures, were successfully fabricated using a humidity-controlled Breath Figure (BF) strategy coupled with crystallization-driven self-assembly. We demonstrate that systematically elevating relative humidity (RH) from 60% to 99% triggers a critical thermodynamic shift from a nucleation-and-growth mechanism to spinodal decomposition. This transition plays a decisive role in driving the formation of highly organized, hierarchical macromolecular structures. Within this framework, TiO₂ nanoparticles serve as potent heterogeneous nucleating agents, effectively directing the radial assembly of PLLA microfibrils and significantly enhancing the matrix crystallinity to 57.0%. As a result, the resulting straw-bundle-like surfaces exhibit robust super-hydrophobicity, characterized by a water contact angle of 153.5° and a low thermal conductivity of 44.5 mW m^-1 K^-1. Most significantly, the optimized hierarchical membranes demonstrated superior passive anti-icing performance, achieving a fascinating icing delay time of 1931 s at -30 °C, a nearly 9-fold improvement compared to disordered flower-like morphologies. This work provides a scalable, sustainable strategy for designing high-performance biopolymer-based anti-icing materials through the synergistic regulation of phase separation kinetics and crystallization behavior.