Study on the formation of carbon nanotube plate using low molecular smectic liquid crystals

Abstract

We present a simple method for preparing carbon nanotube plate(CNT-plate) using self-assemble ability of low molecular smectic liquid crystals. The LCs, 4’-hexyloxy-biphenyl-4-carboxylic acid ethyl ester (C6), was synthesized by simple procedure for the lakylation and the pristine single walled carbon nanotubes was purified and cut for further investigation. The smectic liquid crystal is found to act as a self-assemble template for the formation of CNT-plate. The induced self-organizing CNT-plate is attributed to π-π stacking between hexagonal rings of CNT wall and biphenyl group in C6 and strong intermolecular forces of smectic liquid crystals due to positional and orienational order. From a series of experiments, we could find director distortion of liquid crystals in the vicinity of CNTs during the process. This was confirmed by polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Scanning electron microscopy is used for direct visualization of CNT-plate. Various CNT-plates were observed in the form of randomly oriented bundles as well as uniformly oriented bundles. In addition, stacked CNT-plates, showing lamellar structure of them, were found from cross-section experiment. As far as we know, this is first time using smectic liquid crystal to study on carbon nanotube behavior. We provide another potential possibility for control CNTs.