In-situ graphene alignment in self-sealing stretchable films for efficient thermal interface materials

Although graphene nanoplatelets (GnPs) and carbon nanotubes (CNTs) are known to have demonstrated significant potential as functional fillers to improve the electrical and thermal properties of polymers, aside from the state of dispersion, the level of improvement has been found to be strongly correlated with the in situ orientation. However, achieving in situ orientation within a polymer presents significant technological challenges. In this paper, we show a simple and repeatable thermoforming process to fabricate high thermal conductive GnP nanocomposite pads using a self-sealing stretchable film (parafilm, PF). The pads could be sliced and reoriented into vertical stacks and fused into new pads due to self-sealing nature of PF. Hybrids pads were also constructed with MWCNTs. Vertically aligned hybrids featured thermal conductivities close to 6 W mK(-1) that could be effectively modeled by Maxwell-Garnett (MG-EMA) theory. Vertical alignment also improved bulk (volume) electrical conductivity to 0.1 S cm(-1). Moreover, MWCNTs have exceedingly enhanced the ductility and elongation at break values of GnP nanocomposites that justified their incorporation into the nanocomposites. These hybrids can be easily adapted to various thermal management applications either in the form of freestanding thick pads (1-3 mm) or thermal coatings due to the self-sealing nature of the matrix.