Synthesis and properties of biodegradable polycaprolactone/polyurethanes by using 2,6-pyridinedimethanol as a chain extender

In this study, 4,4′-diphenylmethane diisocyanate (MDI) and poly(ε-caprolactone) diol (PCL) were used to prepare a prepolymer and then 2,6-pyridinedimethanol (2,6-PDM) was used as a chain extender to prepare a new polyurethane, PCL/PDM-PUs. FT-IR analysis confirms the successful synthesis of PCL/PDM-PUs. TGA, DSC and DMA results show that thermal resistance, Tg and dynamic Tg of the compound increase with increasing 2,6-PDM content. Stress-strain curves for the PCL/PDM-PUs show that the tensile strength and elongation at break raise with increasing 2,6-PDM content, whereas Young's modulus decreases with increasing 2,6-PDM content. XRD patterns indicate that polymer chains of the amorphous compound can be more orderly arranged by the presence of higher 2,6-PDM content, although the morphology is still amorphous. Moreover, the swelling degree in aqueous ethanol solution and the hydrolytic degradation rate increase with increasing PCL content. SEM images show that during the degradation period, the original wrinkled surface of PCL/PDM-PUs became smoother first, and then cracks were formed later. The cracks became more severe when subjected to higher temperature.