CO2-derived functional polycarbonates as a sustainable platform for photosensitive polymeric materials

Abstract

The development of CO2-based polymers integrating photo-responsiveness, synthetic versatility and processability remains an important challenge in polymer chemistry. Herein, a modular strategy was developed for multifunctional CO2-derived photosensitive polycarbonates. Catalytic copolymerisation of CO2 and 1,2-epoxy-4-vinylcyclohexene using tetrapyrrolic macrocyclic metal complexes (Cr porphyrin or Al phthalocyanine) as dual-function catalysts and integrated photosensitisers afforded polycarbonates with high carbonate incorporation (95-99%) and preserved photophysical features. Pendant vinyl groups enabled post-polymerisation modification, through an unprecedented Rh-catalysed hydroformylation introducing formyl groups with remarkable chemo- and regioselectivity, while bromination with Br2 provided an additional functionalisation route. Comprehensive structural, spectroscopic and thermal characterisation confirmed the robustness and tunability of the materials. Notably, the Al-phthalocyanine-based polycarbonates retained key photophysical properties of the photosensitiser (φF up to 0.46, φΔ up to 0.21). To overcome polymer brittleness, an ethyl cellulose-based biocomposite film incorporating the formyl-functionalised polycarbonate was prepared, leading to improved flexibility and thermal stability. The formyl-functionalised polymer and the corresponding biocomposite film exhibited strong photo-antibacterial activity, completely eradicating Staphylococcus aureus (≥7-log CFU reduction) under red light (660 nm, 49 J·cm-2), highlighting the potential of CO2-derived photosensitive polycarbonates for light-responsive environmental applications.