Fully Bio-Based Polyhydroxyurethanes with a Dynamic Network from a Terpene Derivative and Cyclic Carbonate Functional Soybean Oil

Polyhydroxyurethanes (PHUs), polyurethanes with excellent properties, are cured without poisonous isocyanate. The carbamate groups in the structure can undergo bond exchange in the presence of amino groups to improve their reprocessing and recyclability. As the demand for more "sustainable" polymers increases, research has focused on replacing fossil materials with renewable alternatives. 1,8-Menthane diamine (MDA) derived from turpentine is a potential raw material for curing with cyclic-carbonated soybean oil (CSBO) for preparing fully bio-based PHUs without solvents and catalysts. The amino groups from MDA facilitate bond exchange under autocatalysis in PHUs, and the rigid structure improves the thermal and mechanical properties of PHUs. PHUs with different cyclic carbonate/amino ratios are characterized to explain the importance of MDA in the performance of PHUs. Dynamic covalent bond exchange was studied through stress relaxation, which results in self-healing, recyclability, reprocessing, and shape memory. The mechanical properties and thermal stability can be almost completely recovered (>85%) after reprocessing several times, indicating that the network will be repaired by bond exchange. This work provides a promising strategy to utilize sustainable feedstocks for designing fully bio-based non-isocyanate polyurethanes and reveals the effect of the structure on the material properties.