Alignment and disorganization of liquid crystals with carbon nanotubes aligning surfaces for novel applications

Abstract

The structural characteristics of carbon nanotube (CNT) make them new interesting aligning layers for liquid crystals (LCs). These highly elongated nanoparticles have surface on which LC strongly anchor and with the use of CNTs sheets, continuous films of aligned CNTs can be easily obtained. Despite the fact that CNT sheets are inhomogenous layers since the linear networks of nanotubes cover partially the plane with gaps, of different distance, in the perpendicular direction and that their degree of orientational order can vary locally, with values well below 1, nematic LCs are oriented by the CNTs along their direction of alignment. The alignment of the LC can be clearly affected by the chosen geometry, as studied with symmetric and asymmetric boundary conditions. Certain alignment could be recognized even with only one aligning surface but two are needed for better and more uniform alignment. The orientational order of CNTs was measured by the anisotropic absorption and found being dependent on the processing steps that decrease its value. Higher value of orientational order of the CNTs seem to be relevant for improving the LC alignment even in the case of use of inorganic coatings of CNTs. With simple assemblies, using two substrates or a single one coated even with one CNT sheet, novel LC applications can be realized such as carbon nanotube-based flexible LCDs or pressure sensors.