Photocatalytic Functionalization of iPP under UV and Mild Conditions: From Direct Surface Activation to Blend Compatibilization

Abstract

Post-polymerization C(sp3)–H functionalization of isotactic polypropylene (iPP) represents a key strategy to overcome its inherently nonpolar nature and enhance interfacial compatibility, yet conventional methods remain limited in material quality. Here, we report an alternative approach to functionalize both solid iPP surfaces and molecular iPP chains using a UV-driven photocatalytic method under mild conditions. We demonstrate that this strategy, performed at 25 °C and under aerobic conditions in the presence of maleic anhydride (MAH), transforms iPP surfaces into polar analogues, with the polar component of the surface energy reaching up to 20 mN/m and exhibiting excellent shelf-life stability over several months. Complementary, the modified synthetic protocol applied to iPP gels at 50 °C under inert conditions enables the synthesis of high-molecular-weight iPP-graft-MAH at functionalization levels of approximately 1 MAH per chain with only marginal chain scission. This process is regioselective to tertiary carbons and favors the functionalization of longer chains, providing conceptual advantages over industrial references. We demonstrate the processability of the resulting products and the mechanical property enhancements when used as phase compatibilizers in blends with polycaprolactone and natural wood.