Sustainable plasma-polymerized poly(ethylene glycol)-like coatings with nitrogen-rich functionalities for antibacterial food packaging applications

Currently, there is a rising interest in the advancement of antibacterial polymer-based food packaging materials, with the goal of enhancing the longevity of packaged food items. The industry is actively seeking environmentally friendly and straightforward techniques for creating the necessary polymeric films with advanced functionality. In line with this, the current study is centered on the fabrication of antibacterial PEG-like coatings that are enriched with nitrogen-containing groups. This is achieved through an aerosol-assisted atmospheric pressure plasma polymerization technique using tri(ethylene glycol) divinyl ether as precursor. To attain this, nozzles with various geometries were employed at the periphery of the plasma head. This nozzle arrangement was instrumental in altering the deposition process and controlling the duration for which the monomer remains within the plasma. As a result, the incorporation of nitrogen-containing functional groups could be achieved directly during PEG plasma polymerization. The findings clearly demonstrate that the use of nozzles exerts a critical influence in shaping the physicochemical properties of the deposited PEG-like coatings. This influence arises from alterations in gas dynamics and residence time of monomer in plasma. By optimizing the monomer residence time, it becomes possible to produce smooth and conformal coatings that exhibit high hydrophilicity, retain PEG functionality, and contain nitrogen-containing functional groups. These latter coatings have demonstrated remarkable antimicrobial activity against E. coli (resulting in a 4.8 log reduction) and S. aureus (with a 2.1 log reduction), primarily due to the existence of nitrogen-rich functionalities on the coating surface. Plasma-polymerized PEG coatings with nitrogen-rich functionalities show promise as effective antimicrobial films for food packaging applications.