Constructing conductive composites by spinodal decomposition of miscible polymer blends with graphene nanoplatelets

Conductive polymer composites (CPCs) enjoy broad industrial applications such as electrostatic discharge (ESD) protection. Herein, we construct CPCs by solution-blending graphene nanoplatelets (GNPs) in a miscible blend of poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN). By inducing PMMA/SAN spinodal decomposition via annealing above the lower critical solution temperature (LCST), we obtain spatially regular, cocontinuous polymer domains where high aspect ratio GNPs preferentially localize within the SAN phase to form a conductive network. Compared to the traditional CPC manufacture approach of blending carbon black into a homopolymer, our approach lowers the percolation threshold required to enhance electrical conductivity. At 1 wt% GNP loading, our blend shows a bulk electrical conductivity of up to ~10^–8 S/cm upon phase separation, suitable for ESD protection. To understand the structure-property relations of our CPCs, we develop TEM image analysis methods to quantitatively characterize the final PMMA/SAN/GNP blend morphology and GNP localization, allowing us to address important questions such as how the state of GNP dispersion within the blend affects the coarsening length scale and domain size distribution throughout the composite.