Upcycling of Silicone Rubber into Value‐Added Polyborosiloxane via Boron‐Assisted Mechanochemistry

Abstract

ABSTRACT Silicone rubber is indispensable in modern life owing to its exceptional thermal resistance, chemical inertness and long‐term stability. However, the robustness of its Si–O–Si backbone makes it among the most difficult materials to recycle, leading to persistent waste accumulation and serious environmental concerns. Herein, we report a boron‐assisted thermomechanical scission (BATS) upcycling strategy that directly converts crosslinked silicone rubber waste into high‐value polyborosiloxane (PBS), a classic strain‐rate‐responsive material known as Silly Putty. Under mild conditions, BATS cleaves Si–O–Si backbones and reconstructs them into dynamic Si–O–B linkages, transforming silicone rubber waste into a high‐value dynamic polymer through a solvent‐free, byproduct‐free process. Because this boron‐assisted scission process acts directly on siloxane chains, it is broadly applicable to diverse silicone rubber wastes and can be implemented using conventional polymer‐processing equipment. Moreover, the resulting PBS exhibits practical utility in impact protection and rate‐responsive sensing. To the best of our knowledge, the BATS strategy appears to be the first example of direct polymer‐to‐polymer upcycling of silicone rubber waste into a substantially higher‐value material. This work establishes a general, scalable, and sustainable polymer‐to‐polymer upcycling platform for silicone rubber waste and offers a promising strategy for advancing a circular organosilicon economy.