Toward sustainable upcycling of vulcanized rubber: advances, applications, and future directions in polybutadiene-based materials

• A comprehensive overview of vulcanized rubber upcycling strategies based on recently reported studies within 2025. • Emphasis on polybutadiene-based waste and tire-derived elastomers. • Covers valorization routes: oxidative, metathesis, catalytic, and thermal. • Identifies current limitations: feedstock heterogeneity, harsh conditions, and poor reintegration. • Outlines future pathways for scalable, circular-material solutions in polymer science. As of 2025, the upcycling of vulcanized rubber has emerged as a critical focus in sustainable polymer science, driven by mounting environmental concerns and increasing volumes of end-of-life elastomers, particularly from waste tires. Due to their permanent crosslinked networks and complex additive compositions, vulcanized rubbers remain resistant to conventional recycling. Recent advances have demonstrated promising strategies for their chemical transformation into value-added materials such as activated carbons, electrochemical components, structural composites, and polymeric intermediates. This review consolidates developments in oxidative degradation, pyrolysis, metathesis chemistry, and covalent adaptive networks, with a focus on polybutadiene-based materials. Process limitations, such as feedstock heterogeneity, harsh reaction conditions, and limited circular reintegration, are critically evaluated. Looking ahead, enhanced mechanistic understanding and tailored upcycling pathways are needed to bridge the gap between laboratory research and scalable, sustainable solutions.