Structural features that control hydrophobicity generation on PLA surfaces

Controlling the wettability of polylactic acid (PLA) surfaces remains a compelling challenge, as this multifunctional biopolymer is widely used in diverse applications and constitutes one of the most employed polymers in additive manufacturing. However, it is often overlooked that PLA is not a single polymer but a family of polymers whose properties vary significantly with the content of the D-isomer. In this work, we aim to rationalize the influence of polymer chain structure on the surface wettability of films prepared from PLA. Five commercial PLA samples were studied to evaluate the influence of D-isomer content and molecular weight on their semicrystalline morphology. Based on these findings, the polymers were processed into films and subjected to a solvent treatment sequence with acetone and ethanol designed to promote crystallization and, consequently, generate surface roughness. The resulting topography and roughness parameters, characterized by profilometry, were correlated with the wettability regime developed on the surface, namely superhydrophobic or parahydrophobic. In addition, the mechanical stability of the rough structures and the durability of the hydrophobic behavior were assessed through friction and water immersion tests, respectively. The results highlight a direct relationship between the D-isomer content and the wetting behavior that can be induced on a PLA surface.