(142d) Stability of Carbon Nanotube Dispersions with a Mixture of Nonionic and Ionic Surfactants in DPD Simulation

Carbon nanotubes (CNTs) have provided a wide range of potential applications over the past few years. However, pristine CNTs tend to agglomerate in solvents because of strong Van der Waals attraction [1].  Investigating ways to disperse CNTs in solutions has been an active research area. In experiments at the University of Oklahoma, the mixture of ionic (Alfoterra) and non-ionic (Tergitol) surfactants have been used to  successfully disperse CNTs in water. Based on this finding, Dissipative Particle Dynamics (DPD) simulations are used to figure out the assembly and the surfactant adsorption on the CNT surface.  First of all, the DPD interaction parameters for surfactants were validated by determining CMC of surfactants from DPD calculations in equilibrium. The micelle shape of each surfactant and the mixture of two surfactants in water were also determined. After that, a CNT (i.e., a hollow carbon cylinder in the simulation) was inserted into the system of water and surfactants. The competition of forming micelles and adsorption on the CNT surface was observed in DPD simulation. Surfactants on CNT make the CNT surface to be more hydrophilic and repel other surfactant molecules at high concentration. Besides, the effect of CNT on surfactant CMC and adsorption density of surfactant was also investigated. Our work can give a more detailed understanding of the configuration of surfactants on the CNT surface and the conditions necessary for the development of stable CNT dispersions.

ACKNOWLEDGEMENTS

The financial support of the Advanced Energy Consortium (AEC BEG08-022) and the computational support of XSEDE (CTS090017) are acknowledged.

REFERENCES

1. L. A. Girifalco, M. Hodak, R. S. Lee, Phys. Rev. B, 2000, 62, 13101-13110.