Castor oil-derived polyurethane networks multiple recyclability based on reversible dynamic acetal bond

Abstract

Making polyurethanes (PUs) from castor oil (CO) is severely constrained because they cannot be recycled due to the irreversibly cross-linked structure. In addition, a CO-derived PU shows low strength, poor durability and inadequate utility because of its elevated cross-linking density and its soft backbone. To overcome this, using a solvent-free thiol-olefin click reaction, we initially synthesized castor oil that has been modified to become 1-thioglycerol (TCO), and then we employed this polyol to produce cross-linked polyurethanes designated TCO-NCO (NCO-HDI, HMDI, and IPDI) without adding a catalyst or solvent. They showed substantial tensile strength that was significantly greater than previously highlighted vegetable oil polyurethanes but were not recyclable. Then we developed VTCO, a combination of vanillin and TCO that occurred at an elevated temperature while the solvent and catalyst remained present. Thereafter, VTCO-NCO was employed to achieve sustainable polyurethane covalent adaptable networks (CANs) that seemed to have new reversible acetal bonds. The PUs have a high rate of stress relaxation because their structural cross-linking network is made up of dynamic acetal bonds. This research introduces a simple, ubiquitous approach that can reconcile mechanical robustness, recycling performance, chemical degradation, and an environmentally friendly way to make sustainable PUs.