Bio-based poly(hydroxyurethane)s of good thermal/mechanical properties upon insertion of polyamide segments

Abstract

Polyaddition of cyclic carbonates (CCs) and di- or polyamines to prepare polyhydroxyurethanes (PHUs) has been regarded as the most promising method to prepare non-isocyanate polyurethanes (NIPUs), granted it incorporates bio-based raw materials and achieves 100 % atom economy. However, low molar mass of bio-based linear PHUs leads to poor mechanical properties and heat resistance, greatly limiting their large-scale production and application as a substitute for conventional polyurethanes. In this study, a di(cyclic carbonate) with hexanediamide segments (HDADCC) was synthesized through a green transesterification of the di(1,2-diols) with dimethyl carbonate under mild reaction conditions. Furthermore, a series of bio-based diamino-terminated oligoamides (DAPADs) were prepared from bio-based dimer acid and decanediamine, effectively increasing the molecular weight of PHUs. Thermoplastic polyhydroxy(amide-urethane)s (PHAUs) were synthesized from the polyaddition of HDADCC with DAPADs. Notable polar difference between diamide segments and bulky alkyl groups resulted in nano-scale microphase separation and highly hydrophobic surfaces for PHAUs. The symmetrical diamide segments enhance the intermolecular forces of materials, while the flexible segments of DAPAD impart excellent toughness. As a result, the newly prepared PHAUs show excellent and tunable thermal and mechanical properties with the tensile strength and elongation at break reaching 19.4 MPa and 560.1 %, and a melting point of up to 100.7 °C. Essentially, this simple and efficient preparation method not only achieves green preparation of polyurethanes but also ensures good mechanical properties and heat resistance, providing a new perspective on the combination of excellent performance and environmental friendliness of polyurethane materials.