Abstract
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.