Recyclable bio-based crosslinked polyurethanes with self-healing ability

We report the synthesis of a linear bio-based polyurethane (bio-PU) containing furan ring by using renewable polylactide copolymer diol and 2,5-furandimethanol as a soft segment and chain extender, respectively, in which the reversible crosslinked covalent bonds between hard segments were incorporated via Diels-Alder (D-A) reaction between the furan ring of the chain extender and bismaleimide (BM) crosslinker. By simply controlling the amount of BM, mechanical properties of the obtained crosslinked bio-PUs (CBPUs) were varied widely. In particular, the CBPU100 sample shows the highest tensile strength of 10.8 MPa, Young's modulus of 193 MPa, and an elongation of 155%. The differential scanning calorimetry experiments verify the recycle property of the CBPUs by the D-A/retro-D-A reaction at the proper temperature. The thermal recyclability and remolding ability of these materials are demonstrated by two kinds of polymer processing methods, i.e., solution casting and hot-compression molding. The recycled CBPUs display almost identical elongation and slightly decreased tensile strength compared to the as-synthesized samples. Furthermore, the CBPUs also exhibit excellent self-healing ability. Therefore, the resulting CBPUs possess tunable mechanical properties, good thermal recyclability, re-mending, and self-healing ability, which makes the bio-based materials more eco-friendly. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46272.