Easily sortable PHBH films functionalized via a magnetic Layer-by-Layer coating deposition

This work presents an eco-friendly and easily scalable process to modify the surface of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) films, a bioplastic of relevant application interest, making them magnetically active while preserving the intrinsic properties of the polymer. To achieve this, ∼10 nm spinel iron oxide magnetic nanoparticles (MNPs), synthesized via coprecipitation method, were assembled using Layer-by-Layer (LbL) deposition with two bio-sourced polyelectrolytes: DNA (polyanion) and chitosan (polycation). An aminolysis reaction was employed to strengthen the interactions between the polymer substrate and the first coating layer. Additionally, the optimal reaction time was determined to maximize surface amine functionalization while minimizing film degradation. The effectiveness of the deposition was demonstrated by both the linear growth of the LbL assembly on a model silicon substrate using FT-IR measurements and by studying the morphology of the coated PHBH films through FE-SEM. These latter measurements showed the formation of a uniform coating after the deposition of 10 bilayers (BL). The 10 BL coated films demonstrated efficient magnetic separation from a mixed polymer waste scraps under a static applied magnetic field. Moreover, these materials undergo enzymatic degradation, with the MNPs that could be easily recovered from the enzymatic solution via magnetic separation, enabling their potential reuse. The proposed approach offers an alternative strategy aimed at tackling the issue of plastic contamination and material sorting during recycling.