A bicyclic carbonate with diamide unit and its tough and strong bio-based linear non-isocyanate polyurethanes containing polyitaconamide sequences

Abstract

Under the background of sustainable development in polyurethane field, the aminolysis of cyclic carbonates (CCs) is one of the most promising and competitive ways to prepare non-isocyanate polyurethane (NIPUs). Nowadays, most of the 5-membered CCs are synthesized by a catalytic cyclocarbonation of epoxides with CO₂. In this study, a new dicyclocarbonate with a hexanediamide unit (HDADC) was prepared through a CO₂-free green route. A hexanediamide tetraol (HDATL) was synthesized first by the amidation of dimethyl adipate (DMA) with 3-amino-1,2-propanediol (3-APDL), and then HDADC was prepared by the cyclocarbonation of HDATL with excess ethylene carbonate (EC). Four bio-based linear NIPUs containing polyitaconamide (PIA) sequences (L-NIPUs) were prepared via a solvent-free and catalyst-free aminolysis of HDADC with H₂N-terminated PIA prepolymers. The L-NIPUs exhibited tensile strength up to 27 MPa and the maximum elongation at break of 392 %. Easy hydrogen bonding of the hexanediamide and flexible PIA segments made the L-NIPUs show excellent toughness and high mechanical property. An efficient and green route was established to synthesize hexanediamide dicyclocarbonate from DMA, 3-APDL, and EC under normal pressure. Bio-based L-NIPUs were prepared and showed good mechanical property.