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

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 (T_g) of PPC is detected when the GO content is below 10 wt %, corresponding to a slightly confined system, whereas two distinct T_g'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 T_g's for a highly confined system. More importantly, it is interesting to find that the switch temperature (T_sw) evolves linearly with the programing temperature (T_prog) for both slightly and highly confined systems, with T_sw ≈ T_prog for a highly confined system but T_sw < T_prog 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.