Bio-based tough hyperbranched polyurethane-graphene oxide nanocomposites as advanced shape memory materials

A fast and simple approach for the large scale fabrication of highly flexible castor oil-modified hyperbranched polyurethane (HPU)-graphene oxide (GO) nanocomposites with high toughness is reported. Three different wt% (0.5, 1 and 2) of GO are incorporated into a HPU matrix to prepare uniformly dispersed GO-based nanocomposites. The performance studies show a tremendous enhancement of the toughness (2540 to 6807 MJ m(-3)) as well as the increment of tensile strength (7 to 16 MPa), elongation at break (695 to 810%) and scratch hardness (5 to 6.5 kg) on the formation of the nanocomposites with 2 wt% GO. The Halpin-Tsai model suggests the 3D random distribution of GO in the HPU matrix. Thermal properties such as thermostability, melting point, enthalpy, degree of crystallinity and glass transition temperature (Tg) etc. of the nanocomposites are correlated with their shape recovery (similar to 99.5%) and shape fixity (similar to 90%) behaviour. Thus, HPU-GO nanocomposites have the potential to be used as advanced thermo-responsive shape memory materials.