The effects of grafted amine groups on the elastic properties of single-walled carbon nanotubes

The molecular dynamics method is used to investigate the effect of amine grafts on the elastic properties of armchair (5,5) (10,10) and zigzag (9,0) (18,0) single-walled carbon nanotubes (SWCNTs). The results show that Young's moduli of armchair (5,5) (10,10) and zigzag (9,0) (18,0) SWCNTs with no grafts are 948 GPa, 901 GPa and 804 GPa, 860 GPa, respectively. When the SWCNTs are grafted with 2-8-amine functional groups, Young's moduli of the zigzag SWCNTs decrease slightly. An increase in the graft number does not cause any further reduction in the moduli, which remain at about 95% of those without grafts. The armchair SWCNTs behave somewhat differently. When they are initially grafted with amine functional groups, their Young's moduli drop quickly; but decrease slowly as the number of grafts increases. When the number of grafts exceeds 6, the moduli remain at about 72% of those without grafts. The results indicate that the effects of grafted amine on the elastic properties of SWCNTs are related to their chiral angle. This phenomenon is analyzed according to the law of the isoline structure of deformation electron density, C-C bond-length, and the system deformation potential energy of carbon nanotubes with different graft numbers. © 2008 Elsevier Ltd. All rights reserved.