Increased dispersion and solubility of carbon nanotubes noncovalently modified by the polysaccharide biopolymer, chitosan: MD simulations

In order to explain the solubility of carbon nanotubes (CNT), including single walled CNTs, wrapped with chitosan of a 60% degree of deacetylation, MD simulations were applied to represent three chitosan concentrations, using two pristine CNTs (pCNT-pCNT), and one and two CNTs wrapped (pCNT-cwCNT and cwCNT-cwCNT). The CNT aggregation was observed in pCNT-pCNT and pCNT-cwCNT due to van der Waals interactions between tube-tube aromatic rings, and inter-CNT bridging by chitosan, respectively. At higher chitosan concentrations, such that most to all of CNTs were wrapped with chitosan, charge-charge repulsion was found to separate robustly the cwCNTs and lead to a well dispersed solution. (C) 2011 Elsevier B.V. All rights reserved.