Yuan Jinkai, Luna Alan, Neri Wilfrid, Zakri Cécile, Schilling Tanja, Colin Annie, Poulin Philippe
Centre de Recherche Paul Pascal, CNRS, Université de Bordeaux, 115 Avenue Schweitzer, 33600 Pessac, France.
University of Bordeaux, CNRS, Solvay, LOF, UMR 5258, 33608 Pessac, France.
Nat Commun. 2015 Nov 16;6:8700. doi: 10.1038/ncomms9700.
Graphene flakes with giant shape anisotropy are extensively used to establish connectedness electrical percolation in various heterogeneous systems. However, the percolation behaviour of graphene flakes has been recently predicted to be far more complicated than generally anticipated on the basis of excluded volume arguments. Here we confirm experimentally that graphene flakes self-assemble into nematic liquid crystals below the onset of percolation. The competition of percolation and liquid crystal transition provides a new route towards high-k materials. Indeed, near-percolated liquid-crystalline graphene-based composites display unprecedented dielectric properties with a dielectric constant improved by 260-fold increase as compared with the polymer matrix, while maintaining the loss tangent as low as 0.4. This performance is shown to depend on the structure of monodomains of graphene liquid-crystalline phases. Insights into how the liquid crystal phase transition interferes with percolation transition and thus alters the dielectric constant are discussed.
具有巨大形状各向异性的石墨烯薄片被广泛用于在各种异质系统中建立连通性电渗流。然而，最近预测石墨烯薄片的渗流行为比基于排除体积论点通常预期的要复杂得多。在这里，我们通过实验证实，石墨烯薄片在渗流开始温度以下自组装成向列型液晶。渗流和液晶转变的竞争为制备高介电常数材料提供了一条新途径。实际上，接近渗流的液晶基石墨烯复合材料显示出前所未有的介电性能，其介电常数与聚合物基体相比提高了260倍，同时保持损耗角正切低至0.4。这种性能取决于石墨烯液晶相单畴的结构。文中讨论了对液晶相变如何干扰渗流转变并进而改变介电常数的见解。
