Self-Seeded Nucleation of PET in a Benign Solvent Yields a High Modulus Aerogel With Ultra-Low Thermal Conductivity

Poly(ethylene terephthalate) (PET) is the most recycled plastic; however, upcycling of this commodity polymer to value-added products has remained limited. Recent attempts to produce PET aerogels have relied on toxic solvents, chemical conversions and cross-linking, and reinforcement to achieve useful mechanical performance. Now, using a new benign solvent (1,3-diphenylacetone), we report a simple, safe, and sustainable dissolution and gelation procedure to convert waste PET into low density, monolithic aerogels with high mechanical strength (E = 20 ± 2 MPa) and remarkably low thermal conductivity (k = 21.9 to 28.9 mW m^-1 K^-1). The key to this process is controlled crystal nucleation by a self-seeding phenomenon during gelation that establishes a mesoscale fibrillar framework. Our strategy offers a benign sol-gel process to upcycle plastic waste into a new form of pure PET for advanced thermal insulation.