Boosting Natural Rubber Performance by Backbone Rigid Functionalization

Natural rubber relies on irreversible vulcanization to enhance material performance, but the resulting densely crosslinked networks resist breakdown, rendering conventional physical recycling methods ineffective. Developing backbone-level functionalization strategies that simultaneously improve performance and enable controlled deconstruction remains a fundamental challenge. Here we develop a backbone rigid functionalization (BRF) strategy to install rigid, polar cyclobutane units directly into natural rubber via catalyst-free [2+2] photocycloaddition. Incorporation of cyclobutane-fused succinimide units substantially enhances tensile strength and toughness. Simply varying the reaction time enables continuous tuning of material behavior from viscoelastic polymers to elastomers and plastomers. When combined with vulcanization, the polar-functionalized natural rubber yields high-performance thermosets with a five‑fold improvement in stress, Young's modulus and toughness relative to conventional vulcanizates. Notably, the cyclobutane-fused succinimide units undergo force-triggered cycloreversion upon bulk ball-milling, enabling vulcanized rubber with on-demand hydrolytic degradability. This single-step BRF process provides a practical pathway for accessing high-performance rubbers with on-demand degradability.