Enhancing glass transition temperature and mechanical properties of poly (propylene carbonate) by intermacromolecular complexation with poly (vinyl alcohol)

Poly (propylene carbonate) (PPC), a promising biodegradable polymer used in medical materials and packaging, is amorphous with low glass transition temperature (Tg), which limits its application. In order to restrain the segment motion of PPC and improve its Tg, based on the supramolecular science theory, polyvinyl alcohol (PVA) with multi-hydroxyl groups was selected to melt blend with PPC to build a unique physical cross-linked network structure by hydrogen bonding between hydroxyl groups of PVA and carbonyl groups or/and terminal hydroxyl groups of PPC. The interactions between PPC and PVA, and the effects of PVA on Tg, thermal behavior, morphology as well as mechanical properties of PPC/PVA composites were investigated. The shift of νO-H and νCO in FTIR confirmed the formation of intermacromolecular hydrogen bonding between PPC and PVA, which guaranteed the good compatibility between PPC and PVA, and significantly improved Tg from 34.1 °C of neat PPC to 44.0 °C of 70PPC/30PVA. This interaction also improved low-temperature thermal stability of the composite, which did favor to the thermal stability during processing and the final performance of the composites, e.g. the tensile strength increased from 10.5 MPa to a maximum value of 39.7 MPa at room temperature.