Regulating nacre-like reduced graphene oxide based composites with polymer-grafted cellulose nanocrystals to achieve high strength, toughness and electrical/thermal conductivity

Inspired by nacre, nanocelluloses are frequently combined with reduced graphene oxide (RGO) to construct nacre-like composites, but achieving a combination of excellent mechanical, electrical and thermal properties remains challenging. Herein, a new strategy of using polyacrylamide-grafted cellulose nanocrystals (CNC-g-PAM) as both the mortar and reinforcing agent is proposed to construct nacre-like RGO based composites with high strength, toughness and electrical/thermal conductivity. The CNC-g-PAM/RGO composite films were prepared by an evaporation induced self-assembly method and subsequent chemical reduction. The grafted PAM chains on CNCs are crucial for regulating the film structure and properties, as they can interact with oxygen-containing functional groups on GO or RGO through hydrogen bonds to improve interfacial interactions. The optimum 6%-CNC-g-PAM/RGO composite film showed a tensile strength of 296.10 MPa and a toughness of 18.26 MJ m-3, which are 3.31 and 6.92 times those of RGO films, respectively. Moreover, it exhibited good electrical conductivity (sigma, 17 342 S m-1) and in-plane thermal conductivity (K, 39.82 W (m K)-1). In contrast, the 6%-CNC/RGO composite film showed a tensile strength of 102.62 MPa, a toughness of 4.34 MJ m-3, sigma of 10 629 S m-1 and K of 14.03 W (m K)-1. Therefore, this work provides an effective strategy to improve the properties of nacre-like RGO based composites, which can promote their application in flexible electronics.