Nonisocyanate Polyurethanes Originated from Biobased Isosorbide with Good Combined Properties

Polyurethane (PU) is conventionally synthesized via the isocyanate route, which has been widely reported to be hazardous to the environment and humans. Consequently, there is an urgent need to develop an environmentally friendly method for the preparation of nonisocyanate polyurethanes (NIPUs). Herein, a green nonisocyanate synthetic route to polyurethane, originating from dimethyl carbonate, 1,6-hexanediamine, 1,6-hexanediol, and rigid biobased isosorbide is introduced to enhance the mechanical properties and heat deflection temperature of NIPUs. A series of biobased isosorbide nonisocyanate polycarbonate-based polyurethanes (ISPCUs) were synthesized by adjusting the isosorbide content in the hard segments. The results show that the rigid ring structure of isosorbide enhances the mechanical and thermal properties of PU. Notably, the melting point of ISPCUs increased from 93 to 119 °C, and the heat deflection temperature has been enhanced to 85 °C from 41 °C of NIPUs without isosorbide. The mechanical properties improved substantially, especially the tensile strength, which increased evidently from 18 MPa of PU to 65 MPa of ISPCUs. This work provides a method to synthesize biobased NIPUs with exceptional heat resistance and mechanical properties.