Synthesis of reduced octadecyl isocyanate-functionalized graphene oxide nanosheets and investigation of their effect on physical, mechanical, and shape memory properties of polyurethane nanocomposites

Herein, two sets of shape memory polyurethane (PU) nanocomposites comprising 3 and 1 wt% of reduced graphene oxide and reduced octadecyl isocyanate-functionalized graphene oxide nanosheets (named as RGO and R (GO-ISO), respectively) were fabricated by solution casting approach. Fourier transform infrared (FTIR) analysis verified linking of octadecyl isocyanate to GO nanosheets via addition reaction of NCO groups with OH and COOH groups and formation of urethane and amide functionalities. The grafting content was determined through thermal gravimetric analysis (TGA), which was about 15 wt% of R (GO-ISO) nanosheets. The appropriate dispersion of R (GO-ISO) nanosheets compared to R (GO) nanosheets in PU was studied by field emission scanning electron microscopy (FE-SEM). Additionally, better distribution level of R (GO-ISO) nanosheets caused PU/R (GO-ISO) nanocomposites to possess greater modulus and lower elongation at break than PU/RGO nanocomposites. Moreover, PU/R (GO-ISO) nanocomposites showed greater shape memory fixities, due to more effective stress transfer of R (GO-ISO) nanosheets than that of RGO nanosheets.