Development of a functionalized polystyrene platform from packaging waste via Friedel-Craft acylation

Through a circular economy approach, expanded polystyrene (EPS) waste can address the need to develop new low-impact materials suitable for packaging, adhesives, and even protective coatings needed for buildings and works of art. In this study, waste Polystyrene (PS) has been chemically modified with increasing feeds of maleic anhydride (MA), using a Lewis acid as a cationic activator (AlCl₃) via Friedel-Crafts acylation. As a result, a novel library of polymer, renamed PS-MA, was synthesized by developing a “one pot” acylation reaction protocol. Nuclear Magnetic Resonance (NMR) and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) assessed the functionalization of PS with MA. PS-MA physicochemical properties were investigated through Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA), and Size Exclusion Chromatography (SEC), linking the characterization of the crosslinked structure with the functionalization degree. Finally, solubility tests yielded the Hansen Solubility Parameters (HSP) and Teas Triangle solubility windows of the new materials. Noticeably, the new PS-MA can be solubilized in green solvents, making its processability in chemical and industrial applications more sustainable than traditional PS. Overall, a new platform of PS-MA with tunable properties was formulated, which stands as an example of functionalized materials obtained from waste through a sustainable synthetic path, with promising impact in numerous industrial and processing sectors.