Pickering-Stabilized Breath Figure Assembly of CNWs-TiO₂/PLA Porous Films: Synergistic Reinforcement and Functional Grading

(1) Background: The development of biodegradable polymers with enhanced functionality is critical for advancing sustainable packaging technologies. This study addresses the challenge of simultaneously improving the structural rigidity and functional performance of poly(lactic acid) (PLA) materials. (2) Methods: Cellulose nanowhisker (CNW) and TiO₂ nanoparticle (Nano-TiO₂) reinforced PLA porous composite films were fabricated via a nanoparticle-assisted breath figure method. The effects of these hybrid nanoparticles on the morphology, thermal stability, and structure of the resulting composites were systematically investigated. (3) Results: The incorporation of CNWs and Nano-TiO₂ played a dual role: they acted as Pickering-like stabilizers at the water/polymer interface, preventing droplet coalescence and facilitating the formation of a well-defined honeycomb-like porous structure. They also significantly enhanced the relative crystallinity of the PLA matrix from 20.26% to 36.31%, owing to the heterogeneous nucleation effect. Consequently, the mechanical properties were significantly enhanced, with the maximum tensile strength and Young’s modulus increasing by 123.3% and 21.9%, respectively. Furthermore, the composite films exhibited excellent UV-shielding performance, achieving an SR UV-B of 97.6%. (4) Conclusions: The synergistic reinforcement of CNWs and Nano-TiO₂ effectively endows PLA composites with superior mechanical properties and functional protection. These findings establish the CNWs-Nano-TiO₂/PLA composite film as a promising candidate for high-performance smart packaging applications.