Innovative antioxidant PET film obtained by sequential aminolysis and genipin-based functionalization

An effective two-step surface modification of poly(ethylene terephthalate) (PET) films (post-consumer waste) based on its amination by chemical aminolysis with ethylenediamine (5, 10, 20 min) was conducted. After amination, a subsequent reaction with genipin (GP) was performed to prepare PET-NH 2 and PET-NH 2 /GP films with antioxidant properties. This innovative sequential modification is presented for the first time, which combines chemical aminolysis with GP cross-linking. Surface functionalization and cross-linking were assessed by UV-Vis spectroscopy for GP concentration and amino groups quantification. ATR-FTIR and XPS evidenced chemical and elemental composition changes. Surface hydrophobicity/hydrophilicity and morphology were assessed by water contact angle and SEM. NH 2 groups on PET surface increased to 25.2 ± 0.9 NH 2 /nm 2 after 20 min, and after cross-linking, PET films with longer aminolysis times exhibited color changes. ATR-FTIR, XPS, and SEM confirmed the surface modification of PET and the presence of cross-linked GP. After 20 min of aminolysis, PET increased its hydrophilicity (from 79 ± 1° to 46 ± 2°), with a subsequent decrease after GP cross-linking (69 ± 2°). PET-NH 2 /GP films exhibited a higher antioxidant capacity (up to 40.4 ± 2.5%) compared to PET-NH 2 films. The surface-modified PET films represent an eco-friendly and viable alternative to producing advanced materials suitable for the immobilization of bioactive molecules in the context of a circular economy. These results provide the foundation for further research into immobilization of bioactive compounds for the development of innovative materials for biomedicine and food packaging areas (shelf-life enhancement through antioxidant protection).