Effect of Functional Group Topology of Carbon Nanotubes on Electrophoretic Alignment and Properties of Deposited Layer

Thin films of aligned carbon nanotubes (CNTs) have several interesting properties including the ability to transport ions, electrons, and thermal energy. The current study employed molecular dynamics (MD) simulations to determine the effect of varying functionalization topologies of CNTs on their deposition characteristics under applied electric fields of varying strength. The results indicate that the dynamics of CNT alignment along the direction of applied electric field is relatively faster and smoother in case of pristine CNTs compared to that of functionalized CNTs. Considering CNTs of identical length, pristine CNTs are aligned the closest to the direction of the electric field followed by side-functionalized and end-functionalized CNTs with the total alignment time being roughly similar. With increase in the strength of electric field, E, total alignment time decreases and is inversely proportional to E-2. The final alignment angle (theta(infinity)) and extent of oscillatory response in the case of side- and end-functionalized CNTs are diminished. In contrast with the alignment dynamics, the migration dynamics of pristine CNTs, which tend to agglomerate, is slower and shows some discontinuity compared to the functionalized CNTs. Analysis of the final structure of the deposited CNTs indicate that side-functionalized CNTs produce the most uniformly aligned deposit at relatively weaker electric fields followed by end-functionalized, and pristine CNTs, due partly to their greater extent of solvation, and are therefore a better choice for deposition of uniform CNT films on substrates.