Bending Deformation Mechanism and Defective Properties of Liquid Crystalline Carbon Nanotubes in Evaporating Droplets

Abstract

Here, we explore the liquid crystalline behavior of carbon nanotubes (CNTs) through two types of commonly physical parameters (the Frank elastic constants kii (i = 1, 2, 3) in the liquid crystal field that typically describe the nature of molecular orientation, and the Young's modulus E that characterizes the peculiar mechanical properties of CNTs). Droplets of aqueous multiwall carbon nanotube (MWNT) suspensions are evaporated on silica wafer at room temperature in air and the resultant deposits exhibit the hallmark property of liquid crystalline formation, birefringence. And scanning electron microscopic (SEM) characterization further presents the concentric bending arrangement of MWNTs along the circumference at the edge. Then in analogy with liquid crystals, based upon the restraint of circular boundary as in the model of droplets, the CNTs' Frank elasticity is introduced and expresses the relationship with E, showing the dependence of nanotube rigidity and dimensions. By comparing the values of plane parameters k11 and k33, defective properties about CNT-assemblies are provided, with Frank elastic constant anisotropy (k11 ≠ k33) contributing to their various distortion structures in the central core of the defects.