(322g) Dip Coating of Carbon Nanotube Films Containing Highly Aligned Whisker-Like Crystallites
We report the creation of a novel type of carbon nanotube (CNT) film structures; they are obtained by forming controlled biphasic CNT fluids, followed by dip coating and solvent extraction. CNTs are dissolved in superacid at sufficiently high concentration to form liquid crystalline (LC) domains interspersed in an isotropic fluid matrix. These LC domains have peculiar ellipsoidal (acicular) shape; surprisingly, they consist of highly aligned CNTs, likely due to the strong elastic energy (splay and bend) and low interfacial tension in the system. The fluid is deposited onto a glass slide by dip coating, causing streamwise alignment of the anisotropic LC domains; the domains act as ?nucleating sites? for the further growth of large, whisker-like crystallites of aligned CNT during acid removal by solvent extraction. This study shows how self-assembly (phase behavior of CNT in acid) can be combined with directed assembly by flow to produce films with novel structures. Finally, there is scope to modulate the interaction between CNTs and thus solution phase behavior through the use of different acid mixtures with varying acid strength, thereby allowing for the further tailoring of film structure and properties.