Preparation of amorphous nanocomposites with quick heat triggered shape memory behavior

- Nanocomposites of poly(vinyl acetate)/graphene were prepared through the simple solution mixing method.
- The prepared amorphous nanocomposites showed elastic and stiff structure.
- Nanocomposites showed fast heat triggered shape recovery (within 5 s).
- The fixation ratio (Rf) and recovery ratio (Rr) of nanocomposites could be as high as 99.8 and 98.2%, respectively.

The aim of this work was to prepare shape memory materials from poly(vinyl acetate) (PVAc), a low-cost commercial polymer, through the simple solution mixing method without need for complex synthetic routes. However, neat PVAc with inherent low strength and modulus exhibited inappropriate shape memory behavior. Therefore, stiff graphene nanoplatelets were incorporated within the PVAc matrix to improve its thermomechanical properties. Transmission electron microscopy (TEM) observations showed that graphene nanoplatelets built up a dense 3D network throughout PVAc. Furthermore, tensile and dynamic mechanical analysis (DMA) results demonstrated that the strength and modulus of PVAc were noticeably enhanced by introducing graphene nanoplatelets. DMA revealed that the PVAc/graphene nanocomposites possess excellent shape memory properties, as the fixation ratio (Rf) and recovery ratio (Rr) could be as high as 99.8 and 98.2%, respectively, and the original shape recovery time was ∼5 s. The remarkable improvement in the shape memory properties of nanocomposites was correlated to great stored elastic strain energy in nanocomposites providing a high driving force for subsequent quick and almost complete shape recovery. In addition, enhanced heat transfer rate in the presence of graphene network can also account for high speed thermal actuation of the developed nanocomposites.

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