Herbert Gleiter Institute of Nanoscience, Nanjing University of Science & Technology , Nanjing 210094, People's Republic of China.
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University , Nanjing 210009, People's Republic of China.
Langmuir. 2017 Oct 24;33(42):11590-11602. doi: 10.1021/acs.langmuir.7b01973. Epub 2017 Aug 30.
We have infused graphene/ionic liquid into block copolymer homoporous membranes (HOMEs), which have highly ordered uniform cylindrical nanopores, to form compact, dense, and continuous graphene/ionic liquid (Gr/IL) lubricating layers at interfaces, enabling a reduction in the friction coefficient. Raman and XPS analyses, confirmed the parallel alignment of the cation of ILs on graphene by the π-π stacking interaction of the imidazolium ring with the graphene layer. This alignment loosens the lattice spacing of Gr in Gr/ILs, leading to a larger lattice spacing of 0.36 nm in Gr of Gr/ILs hybrids than the pristine Gr (0.33 nm). The loose graphene layers, which are caused by the coexistence of graphene and ILs, would make the sliding easier, and favor the lubrication. An increase in the friction coefficient was observed on ILs-infused block copolymer HOMEs, as compared to Gr/ILs-infused ones, due to the absence of Gr and the unstably formed ILs film. Gr/ILs-infused block copolymer HOMEs also exhibit much smaller residual indentation depth and peak indentation depth in comparison with ILs-infused ones. This indicates that the existence of stably supported Gr/ILs hybrid liquid films aids the reduction of the friction coefficient by preventing the thinning of the lubricant layer and exposure of the underlying block copolymer HOMEs.
我们将石墨烯/离子液体注入具有高度有序均匀圆柱纳米孔的嵌段共聚物均孔膜（HOMEs）中，在界面处形成致密、连续的石墨烯/离子液体（Gr/IL）润滑层，从而降低摩擦系数。拉曼和 XPS 分析证实，ILs 的阳离子通过咪唑环与石墨烯层的π-π堆积相互作用平行排列在石墨烯上。这种排列方式使 Gr/ILs 中的 Gr 晶格间距变松，导致 Gr/ILs 杂化中 Gr 的晶格间距为 0.36nm，大于原始 Gr（0.33nm）。由于石墨烯和 ILs 的共存，松散的石墨烯层使得滑动更容易，有利于润滑。与 Gr/ILs 注入的嵌段共聚物 HOMEs 相比，注入 ILs 的嵌段共聚物 HOMEs 的摩擦系数增加，这是因为缺少 Gr 和不稳定形成的 ILs 膜。与注入 ILs 的 HOMEs 相比，Gr/ILs 注入的嵌段共聚物 HOMEs 的残余压痕深度和峰值压痕深度也小得多。这表明，稳定支撑的 Gr/ILs 混合液体膜的存在有助于通过防止润滑剂层变薄和暴露下面的嵌段共聚物 HOMEs 来降低摩擦系数。
