RESEARCH ARTICLE Copyright © 2013 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Colloid Science and Biotechnology Vol. 2, 1–5, 2013 Structure and Dynamics of a Nonionic Surfactant Within a Carbon Nanotube Bundle by Molecular Dynamics Simulation S. Mahmood Fatemi and Masumeh Foroutan ∗ Department of Physical Chemistry, School of Chemistry, College of Science, University of Tehran, Tehran, Iran We used the MD simulation to examine the behavior of Triton X_100 (TX100) with two nano- structures, namely carbon nanotube (CNT) and CNT bundle. The possibility of wrapping CNT bun- dles was studied and the simulation results demonstrated that the peripheral grooves are preferred sites for the adsorption of Triton surfactant on the surface of CNT bundles. These findings suggested that Triton surfactant conformational behavior could be strongly influenced by geometric constraints of the surface of CNT bundles, so we used a seven open-ended (5,5) armchair CNT bundle with a length of 25 Å in different temperatures. The TX100 morphology to the surface of bundle was investigated by the radius of gyration. The result of the radius of gyration was in agreement with the findings of interfacial binding between bundle and TX100 and showed that the strong intermolec- ular interaction between bundle and TX100 that cannot be influenced by the temperature in the range we reported. These findings suggested that TX100 conformational behavior could be strongly influenced by geometric constraints of the surface of CNT bundles. Keywords: Molecular Dynamic (MD) Simulation, Carbon Nanotubes (CNTs) Bundle, Triton X_100 (TX100) Surfactant, Interaction Energy, Radius of Gyration (R g ). 1. INTRODUCTION CNTs have been examined greatly for several applications due to their unique electrical and mechanical properties. 1 Soon after the revelation of CNTs, 2 attempts were made to seek a bundle of CNT. In 2006 Kang et al. 3 defined a nano- tube bundle as a closely packed array of aligned tubes in a triangular lattice. By denoting one nanotube as the centre of the bundle, hexagonal rings of nanotubes can be defined in the network. CNT Bundle is nanostructures that promise much in the area of constructing nano scale devices due to their enhanced mechanical, electrical and thermal prop- erties. Recently, Cox et al. 4 investigated the mechanics of nanotubes oscillating in carbon nanotube bundles. Also, Kim et al. 5 investigated the effect of the tube diameter dis- tribution on the high-temperature structural modification of bundled CNT nanotubes. Due to the formation of big bundles held strongly together, CNTs are very difficult to disperse homoge- neously in solution. One of the approaches that have been widely used to exfoliate bundles and prepare individual ∗ Author to whom correspondence should be addressed. CNT is the non-covalent wrapping of the tubular sur- face by various species of surfactant. Simulations results 6–8 showed that surfactants tend to wrap around the CNT with more distinct conformations. Surfactants have proven useful in deploying ultracentrifugation techniques for separating carbon nanotubes, but the molecular mecha- nism responsible for the effectiveness for such technique remains not fully understood. On the basis of recent molecular simulation results, it appears that the morphol- ogy of self-assembled surfactant aggregates on carbon nanotubes strongly affects the effective potential of mean force between pairs of interacting carbon nanotubes. The effect of surfactant molecular structure on the properties of aqueous surfactant self-assembled aggregates was investi- gated using all-atom molecular dynamics simulations and the role of surfactant molecular structure on self-assembly has been revealed. 9 In the present work, we concentrate on the micro- scopic and dynamic properties of wrapping CNTs/CNT bundle by TX100 surfactant. MD simulations are con- ducted to explore the interaction between and CNT/CNTs bundle and TX100 and their comparison in various tem- peratures. To the best of our knowledge, there has not J. Colloid Sci. Biotechnol. 2013, Vol. 2, No. 1 2164-9634/2013/2/001/005 doi:10.1166/jcsb.2013.1037 1