Contact-active antibacterial polyethylene foils via atmospheric air plasma induced polymerisation of quaternary ammonium salts

Abstract

Polyethylene (PE) foils were modified with potent contact-active antibacterial quaternary ammonium salts (QAS) by an atmospheric air plasma activation step, followed by graft-polymerisation of vinylbenzyltrimethylammonium chloride (VBTAC) monomers. The presented approach uses a cost efficient air plasma activation and subsequent radical polymerisation in highly concentrated aqueous monomer solutions to generate efficient antibacterial materials. The obtained contact-active poly-VBTAC modified PE foils feature a homogeneous and 300 nm thick polymer layer with a high charge density of approximately 10¹⁶ N⁺/cm². The antibacterial properties were evaluated against Gram-negative (P. aeruginosa, E. coli) and Gram-positive (S. aureus, S. epidermidis) bacteria. The materials showed strong antibacterial activity by eradicating all the inoculated bacteria with bacterial challenges of 10⁴ to 10⁵ CFU/cm² and good reductions even at maximum challenge (10⁸ CFU/cm²). We have confirmed contact-activity by an agar diffusion assay. The obtained materials are therefore highly attractive for applications, for example, in packaging and are a contribution to an ecomic and green antimicrobial management without release of biocides to the environment.

Keywords: Antifouling; Biocides; Contact-active materials; Quarternary ammonium salts.