Incorporation of graphene into polyester/carbon nanofibers composites for better multi-stimuli responsive shape memory performances

Graphene oxide was directly reduced into graphene in N-methyl-pyrrolidone with the assisted-dispersion of vapor grown carbon nanofibers (VGCF), resulting in a homogeneous dispersion of VGCF-graphene hybrid filler (VGCF-G). In the hybrid filler, VGCF served as effective stabilizers for graphene by adsorbing VGCF onto graphene through π-π interaction. Subsequently, the as-prepared VGCF-G was incorporated into a bio-based polyester (BE) to prepare BE/VGCF-G composites by solution blending. In the composites, graphene was complete exfoliated with the assisted-dispersion of VGCF. Simultaneously, graphene acted as "compatibilizer" to improve the dispersion of VGCF and enhance the interfacial adhesions. As a consequence, the binary combination of VGCF and graphene showed remarkable synergistic effects in improving the electrical conductivity and mechanical properties of the BE/VGCF-G composites. For example, at the filler content of 4.8 vol%, the electrical conductivity of BE/VGCF-G composite is about 4 orders of magnitude higher than BE/VGCF composite containing VGCF alone, and the ultimate stress and modulus of BE/VGCF-G composite is 58% and 45% higher than those for BE/VGCF composite. Furthermore, multi-stimuli responsive shape memory performances (electro-activated and infrared-triggered) of the composites were investigated. BE/VGCF-G composites showed a combination of higher shape memory recovery, stronger recovery stress and faster response, compared with BE/VGCF composites.