(316f) Janus Buckypapers: Bilayer Films of Pristine Graphene Stabilized By Pyrene-Functional Copolymers

One of the recurring problems facing graphene-polymer composites is the need for dispersants to allow for stable graphene exfoliation prior to incorporation into composites. These dispersants tend to be counterproductive and are difficult to remove. To meet this need, we have developed a general strategy for modifying target polymer matrices with pyrene-containing side groups; we have previously applied this strategy to siloxanes (Nanoscale, 2014). We now show that this technique may be generalized to other polymers. We present a new approach for preparing novel thin films of melt-processable polymers such as polystyrene (PS) and poly(methylmethacrylate) (PMMA), with one graphene-enriched surface. Random copolymers of 1-pyrenemethylmethacrylate with styrene or methyl methacrylate are prepared by simple, bulk, free-radical polymerizations. After dispersing graphene nanosheets in solutions of these polymeric stabilizers, cast films are prepared, and their electrical properties are characterized for the first time. Applying a leaching approach in conjunction with vacuum filtration increases the overall concentration of graphene in the films, while promoting accumulation of graphene at the surface in contact with the filter. The resulting asymmetric films are the first examples of graphene-containing thin films having widely dissimilar electrical conductivities on the top and bottom surfaces. This report describes the preparation, properties, and possible applications of these "Janus buckypapers," which have one electrically conductive surface and one electrically insulating surface.