PLA-derived lactate esters as plasma precursors for hydrophilic and antibacterial coatings

This study investigates the use of methyl lactate and ethyl lactate, prepared from virgin polylactic acid (PLA) through model chemical recycling, as bio-based precursors for atmospheric-pressure plasma deposition of multifunctional coatings on polyethylene terephthalate (PET). Plasma treatment significantly enhanced surface hydrophilicity, reducing the water contact angle from 76° for untreated PET to 27° for ethyl lactate and 51° for methyl lactate coatings. X-ray photoelectron spectroscopy (XPS) confirmed the incorporation of oxygen- and nitrogen-containing functional groups, while atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed surface morphology changes. The plasma-modified surfaces exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus, achieving up to 3.4 and 2.3 log reductions, respectively, according to ISO 22196:2011. The results demonstrate the potential of lactate esters for hydrophilic and antibacterial plasma coatings and support future recycling-oriented and circular-economy-based plasma surface engineering approaches.