High-Speed Actuation and Mechanical Properties of Graphene-Incorporated Shape Memory Polyurethane Nanofibers

We prepared poly(ε-caprolactone) (PCL)-based shape memory polyurethane (PU) nanofibers incorporating three kinds of graphene, that is, graphene oxide (GO), PCL-functionalized graphene with PCL (f-GO), and reduced graphene (r-GO) to investigate their mechanical and shape memory properties. Incorporation of graphene into the PU nanofibers increased the modulus and breaking stress compared to that of pure PU nanofibers. In particular, the f-GO nanofibers showed the largest enhancement in mechanical properties because of increased interaction between graphene and the polymer matrix. In the shape memory test, f-GO or r-GO-incorporated PU nanofibers showed actuation speed that was much faster than that of pure PU nanofibers. The shape recovery time of 1 wt % f-GO or r-GO nanofibers was 8 s, whereas that of the PU nanofibers and GO-incorporated nanofibers were 27 and 13 s, respectively. This study demonstrates that incorporation of f-GO into shape memory PU nanofibers can be used effectively to achieve both high-speed shape recovery and high mechanical strength.