Multishape and Temperature Memory Effects by Strong Physical Confinement in Poly(propylene carbonate)/Graphene Oxide Nanocomposites

The importance of filler–matrix interactions is generally recognized for mechanical property enhancement; their direct impact by physical confinement on diverse functional properties has remained poorly explored. We report here our effort in achieving versatile shape memory performances for a biodegradable poly­(propylene carbonate) (PPC) matrix containing high contents of graphene oxide (GO). The excellent dispersion in the entire filler range (up to 20 wt %) allows precise morphological tuning, along with physical filler–matrix interactions, contributing overall to a strong nanoconfinement effect that positively affects the thermomechanical properties of nanocomposites. Only one glass-transition temperature (Tg) of PPC is detected when the GO content is below 10 wt %, corresponding to a slightly confined system, whereas two distinct Tg’s are observed with a GO content over 10 wt %, corresponding to a highly confined system. As such, a tunable multishape memory effect can be achieved simply by tuning the filler contents. A dual-shape memory effect (DSME) is observed for a slightly confined system, whereas a triple-shape memory effect (TSME) can be achieved by deformation at two distinct Tg’s for a highly confined system. More importantly, it is interesting to find that the switch temperature (Tsw) evolves linearly with the programing temperature (Tprog) for both slightly and highly confined systems, with TswTprog for a highly confined system but Tsw < Tprog for a slightly confined system. Our work suggests a highly flexible approach to take advantage of the strong nanoconfinement effect by tuning the content of GO within a single polymer to access versatile SMEs, such as DSME and TSME, and the temperature memory effect.