Efficient Synthesis of High-Performance Biobased Nonisocyanate Polyurea Thermoplastic Elastomers Containing Long-Chain Dimer Acid Polyamide Sequences

Abstract

A simple and efficient strategy was developed for the synthesis of high-performance biobased nonisocyanate polyurea thermoplastic elastomers (NIPUrea TPEs) by introducing long-chain dimer acid (DA)-based polyamide (DAPA) sequences and urea linkages. Amine-terminated DAPA prepolymers were first prepared via melt polycondensation of DA with excess hexamethylenediamine or dodecanediamine at various −NH2/–COOH molar ratios and were subsequently chain-extended with ethylene carbonate through in situ urethanization and polycondensation, yielding crystalline NIPUrea TPEs. The incorporation of urea bonds significantly enhanced the melting temperature (up to 109 °C), crystallinity (43–58%), and thermal stability (T5% > 378 °C) of the resulting materials. Moreover, the NIPUrea TPEs exhibited excellent mechanical properties, with tensile strength reaching 39 MPa and elongation at break up to 830%, together with high hydrophobicity and good resilience (200% resilience of 64–81%). Compared with conventional NI-polyureas, which are mostly thermoplastics, the present system provides an efficient isocyanate-free route to prepare crystallizable and fully biobased NIPUrea TPEs with balanced thermal and mechanical performance, aligning with the principles of sustainable polymer chemistry.