Synthesis of polyoxalate diols from dimethyl oxalate through transesterification-polycondensation reaction and their application in preparing novel polyurethane elastomers

Growing environmental awareness greatly promotes the development of transforming coal resources into high-value added chemicals in a diversified, low-carbon and cleaner way. Dimethyl oxalate (DMO) is one of the modern coal chemical products, and it is of great significance to develop its new downstream products. In this work, polyoxalate diols (PODL) were facilely synthesized from DMO and small molecule diols via transesterification and polycondensation reactions. Further, a series of polyurethanes (PU) with excellent mechanical properties, heat resistance (T d > 300°C) and solvent resistance were prepared from polyoxalate diols and 4, 4′-diphenylmethane diisocyanate (MDI). The introduce of oxalate groups featuring a planar conjugated structure into the polyurethane backbone resulted in enhanced chain rigidity and increased hydrogen bond density, leading to a significant improvement in the tensile strength. In particular, PU-PHD-2k shows 44.6 MPa in tensile strength, 535.4% in elongation at break, and 159.0 kN m -1 in tear strength, which can rival and even surpass commercial polyester polyol derived polyurethanes. On the other hand, the oxalate group promotes the aggregation of the hard segments, thereby enhanced the microphase separation. Atomic force microscopy (AFM) and fourier transform infrared spectroscopy (FT-IR) results demonstrate that PU-PHD's superior mechanical properties are attributed to the ordered hydrogen bonds formed in its structure and significant microphase separation between the soft and hard segments. Moreover, PU-PDD demonstrates excellent mechanical strength and degradability, making it potentially suitable for biomedical and agricultural applications. • Polyoxalate diols are synthesized from dimethyl oxalate - an abundant and cost-effective raw material - with a highly efficient catalyst used at low loadings, enabling the transformation of coal resources into high value-added chemicals. • The molecular structure and physical properties of novel polyoxalate diols are determined systematically. • With exceptional mechanical properties, polyoxalate-based polyurethanes can match and even outperform commercial polyurethanes in terms of tensile and tearing strength.