One-step UV-curable ligand copolymer coatings

Polymeric surface photografting is a desirable method to modify the interfacial interactions of inert materials and enable one-step surface functionalisation e.g. antimicrobial, antifouling, bioprinting, and so on. Now, a novel UV-curable lysine derivate ligand copolymer coating was synthesised using surfactant-free emulsion polymerisation for use as a non-migratory antioxidant packaging coating. NMR was used to estimate the ratio of butyl acrylate (47 mol%) and benzophenone moiety (19 mol%) in the copolymer that would be optimal for UV-curable coating on the polypropylene (PP) film surface.

The copolymer, containing 34 mol% of functional monomer, was photochemically grafted onto the PP film surface (365 nm, 90 s), and a large amount of COOH functional groups was detected on the PP film surface (302 ± 19 nM). The chemical and microstructural evaluations of the film confirmed the ligand compositions and grafting morphology of the ligand film (rough surface).

No migrant residue

The ligand film adequately chelated Fe⁺³ (215 ± 26 nM,) in an aqueous solution with pH of 5; this chelation imparted antioxidant properties to the ligand film. Furthermore, the ligand film was stored with virgin olive oil and vitamin C (pH = 7) inoculated with Fe⁺³, which significantly (p < 0.05) retarded the lag time of oxidation and degradation of the product, respectively. The EU migration test proved that this system did not leave any migrant residue, enabling the clean labeling of the system.

According to the researchers, the work bridged the research gap in non-migratory antioxidant packaging by developing a curable biomimetic ligand copolymer using a practical industrial scalable method that can be applied for packaging, cosmetics, and biomedical purposes.

The study has been published in Progress in Organic Coatings, Volume 162, January 2022.