Advanced Polymer Hybrid Materials with Anisotropically Aligned Carbon Nanotubes

Carbon nanotubes (CNTs) have been reported their high tensile strength, electrical conductivity, and thermal conductivity. Even though CNTs are utilized as conductive materials in various fields, the studies are focused on CNT-dispersed conductive sheets. However, the anisotropic property of CNTs enables vertically aligned CNTs to have much higher mechanical strength and electrical conductivity. Despite the versatility of polymers, their applications are limited due to the weak strength and the poor electrical conductivity. Thus, some studies have improved their properties by adding conductive materials like CNTs. Particularly, the anisotropic properties of CNTs can fortify polymers to lightweight hybrid polymers with high strength and electrical conductivity. For this purpose, a method of coating polymers on vertically synthesized CNT forests was suggested, but the process is complicated, and it is very difficult to produce the hybrid polymer of large area. We suggest a much more simple and effective process for anisotropically aligned carbon nanotubes (A-CNT)-polymer hybrid materials. In the pre-polymer solution, mildly oxidized CNTs were arranged in the vertical direction by electrophoresis. Electric fields for the arrangement were formed by alternating currents through indium tin oxide (ITO) electrodes. The polymer was subsequently cured by ultraviolet radiation and the aligned CNTs were fixed in the polymer. The A-CNT-polymer showed higher strength in compression tests compared to the CNT-polymer before the arrangement. In addition, the parallel direction to A-CNT promoted the much lower resistance for the electric current. Low-weight composition of CNTs can efficiently fortify the mechanical and electrical properties of the polymer. The excessive addition of CNTs seems to reduce the mechanical strength of the photocurable polymer. This low-weight and multi-functional hybrid materials can be developed to bodies of vehicles, ballistic materials, or membranes for fuel cells.