Chemically recyclable polyurethanes based on bio-renewable γ-butyrolactone: From thermoplastics to elastomers

The large-scale production and disposal of petroleum-derived commercial polyurethane materials have caused severe enviroment problem. Although the bio-based or biodegradable polyols have attracted considerable attention to prepare sustainable polyurethanes, the chemical recycling of polyurethanes via controlled bond scission reactions to recover monomer or value-added building blocks still remains as a big challenge. In this contribution, we address this challenge by preparation of biodegradable and chemically recyclable polyurethanes using bio-based telechelic hydroxyl terminated poly(gamma-butyrolactone) (P gamma BL) diols as precursors. The obtained polyurethanes exhibited thermoplastic or elatomeric properties depending on the molar mass of used P gamma BL diol precursors. The thermal, mechanical and hydrolytic properties of P gamma BL based polyurethanes are systematically investigated. Remarkably, the polyurethanes are capable of chemical recycling to recover gamma BL with high purity in an almost quantitative yield by a simple vacuum distillation procedure.