Shape memory thin films of Polyurethane: Does graphene content affect the recovery behavior of Polyurethane nanocomposites?

摘要

Thin nanocomposite films of polyurethane have received remarkable attention due to their shape memory properties. As most of the reports focus on the beneficial aspects of the presence of nanofillers such as graphene nanoplatelets (GNPs) introduced into shape memory polymers, some research results reveal the opposite trend. The polyether/polyester-based polyurethane was synthesized through a condensation polymerization and the nanocomposite films containing 0.1, 0.25, 0.5, and 1 wt.% of GNPs were prepared by the solvent casting method. The Fourier transformed infrared (FTIR) spectroscopy was carried out to investigate the chemical structure of nanocomposite films. The properties of nanocomposite films were verified by the differential scanning calorimetry (DSC), X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), tensile test, and the dynamic mechanical analysis (DMA). The shape memory properties were studied through various thermomechanical cycles applied by the DMA apparatus. All the nanocomposite films showed larger glassy storage moduli compared with those of the neat PU films. The nanocomposite film containing 0.25 wt.% GNPs showed the highest shape recovery ratio (92.4%) since the net-point effect of GNPs dominates its slipping effect. While for the other nanocomposite films the slippage effect overcomes the net-point effect.