Direct Polymer-on-Polymer Grafting of Polyolefins under Visible Light

Polyolefins dominate global plastic production but resist chemical transformation, leading to persistent waste accumulation. Developing new strategies that can repurpose these waste materials into higher-value products is therefore essential. Although conventional polar small-molecule grafting improves functionality, the resulting densely substituted polyolefins often become softer materials due to lower crystallinity and strength. Here, we report a visible-light-driven radical method that directly grafts diverse vinyl polymers onto polyolefins without the need for catalysts or initiators. The approach is broadly applicable to both pristine and postconsumer polyolefins on a multigram scale. Despite substantial functionalization that markedly increases polarity, the grafted polyolefins retain crystallinity, thermal stability, and mechanical robustness owing to their sparse yet extended polar polymer side chains. As a proof of concept, we demonstrate exceptional adhesion performance, with shear strengths approaching an order of magnitude higher than those of commercial hot-melt adhesives. This work establishes a general principle for polymer-on-polymer grafting of commodity plastics, expanding the conceptual space of polyolefin modification.