Closed-Loop Recyclable High-Performance Aerogels Derived from Polystyrene

Upcycling of low valuable plastic waste into materials with enhanced properties helps progress toward establishing a plastics circular economy. Furthermore, implementing recyclability as a core design criterium for newly formed materials can significantly increase their impact on sustainability, yet rarely explored. In this work, the upcycling of polystyrene (PS) waste is presented into closed-loop recyclable high-performance aerogels. Through a simple post-functionalization process, PS is aminated to generate a polyfunctional amine, which is then reacted with aldehydes to form a recyclable cross-linked imine network. This network is subsequently dried to produce poly(styrene-imine) aerogels (PSAs). The resulting PSAs exhibit excellent thermally insulating properties, along with low density, outstanding mechanical strength, and intrinsic hydrophobicity. More importantly, these aerogels show quantitative depolymerization under acidic aqueous conditions, back to their original precursors which can be recovered in high yield and purity and reused for the synthesis of fresh aerogels with nearly identical material properties, thus achieving closed-loop recycling. This work presents an efficient method for upcycling of chemically non-recyclable plastics into recyclable and high value-added advanced aerogel materials, offering a new pathway for establishing a circular economy for plastics.