Aqueous-Based Biomimetic Porphyrin-Catalyzed Surface Oxidation of Polyethylenes for Enhanced 3D-Printability

Postsynthetic modification of polyethylenes (PEs) is a powerful emerging strategy for imbuing these high-volume commodity polymers with new properties, enabling their usage in diverse conventionally inaccessible applications. However, the solvent resistance of PEs has posed a long-standing challenge, often necessitating highly hazardous chlorinated and/or aromatic solvents for well-controlled homogeneous-phase reactions. While heterogeneous PE surface oxidations can occur under aqueous conditions, achieving high functional group selectivity is extremely challenging, even when mediated by enzymes. Herein, we show that biomimetic water-soluble vanadium (IV)-porphyrin catalysts allow selective PE surface oxidation in predominantly aqueous solvent media, achieving a carbonyl: alcohol selectivity of at least 5:1 at only 0.03 mol·% catalyst loading. Like enzyme engineering to enhance plastic degradation, we show that augmenting catalyst affinity to the hydrophobic PE surface can lead to a >70% increase in catalytic turnover numbers. The resulting surface-oxidized HDPE shows practical utility by bringing about greatly improved 3D printability compared to unfunctionalized HDPE, allowing low structural warpage, 8 times faster printing speed, and enhanced interfacial adhesion that allows reduction of print bed temperature by 20 °C. Our findings showcase the utility of highly selective PE surface functionalization for enhancing their functional properties, freeing up constraints of polymer solubility for controlled reactive modification.