Quantitative relationship between surface chemistry of graphene and compatibility with rubbers established by two-dimensional solubility parameters.

Hildebrand ( ) and Hansen ( , , ) solubility parameters are important indexes to predict the compatibility of components intuitively. Currently, almost all the experiments only measured the solubility parameters of the pristine graphene. Therefore, there is a lack of quantitative relationship between the surface chemistry of graphene and solubility parameters, resulting in no theoretical guidance for the surface modification of graphene. In this work, three-dimensional Hansen solubility parameters are converted to two-dimensional solubility parameters. Hildebrand and two-dimensional solubility parameters of six functionalized graphene as a function of grafting ratio are calculated by molecular dynamics (MD) simulation. Interestingly, if the functional group is at the edge of graphene, the decreases with the increase of the grafting ratio, whereas if the functional group is in the plane of graphene, the decreases first and then increases with grafting ratio. Two-dimensional solubility parameters are proved to be a good predictor of the compatibility between functionalized graphene and rubbers. The quantitative relationship between the surface chemistry of graphene and compatibility with rubbers based on two-dimensional solubility parameters is constructed. The optimum grafting ratio corresponding to the best compatibility is given. Finally, the effect of temperature on the compatibility behaviors of graphene/rubber mixtures is elucidated.