The stability and dispersion of carbon nanotube-polymer solutions: A molecular dynamics study (original) (raw)

Carbon Nanotube Dispersion in Solvents and Polymer Solutions: Mechanisms, Assembly, and Preferences

ACS nano, 2017

Debundling and dispersion of carbon nanotubes (CNTs) in polymer solutions play a major role in the preparation of carbon nanofibers due to early effects on interfacial ordering and mechanical properties. A roadblock toward ultrastrong fibers is the difficulty to achieve homogeneous dispersions of CNTs in polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) precursor solutions in solvents such as dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF). In this contribution, molecular dynamics simulations with accurate interatomic potentials for graphitic materials that include virtual π electrons are reported to analyze the interaction of pristine single wall CNTs with the solvents and polymer solutions at 25 °C. The results explain the barriers toward dispersion of SWCNTs and quantify CNT-solvent, polymer-solvent, as well as CNT-polymer interactions in atomic detail. Debundling of CNTs is overall endothermic and unfavorable with dispersion en...

Dispersion and rheology of carbon nanotubes in polymers

International Journal of Material Forming, 2008

We review two generic mechanisms of dispersion of carbon nanotubes in a low-viscosity solvent or high-viscosity polymer, focusing on the neat nanotubes not surface-functionalized in any way. We give estimates of the van der Waals energies involved in nanotube aggregates and examine two main techniques: ultrasonication and shear mixing. For ultrasonic dispersion methods, the local mechanical energy applied to individual tubes is high and bundle separation is assured in the cavitation regime. We analyze and estimate the tube scission during ultrasonic cavitation and predict the characteristic nanotube length L lim below which scission does not occur. For shearmixing, our analysis suggests that dispersion is possible in non-parallel bundled nanotube aggregates, in high-viscosity polymers, once a critical mixing time t * is reached. We then examine characteristic features of nanotube-polymer composite rheology and its aging/stability against re-aggregation. We show that at nanotube loading above overlap concentration the tubes form an elastic network in the matrix. Physical junctions of this network are strong and stable enough to provide a rubber-like elastic response with very slow relaxation.

Modeling and simulations of carbon nanotube (CNT) dispersion in water/surfactant/polymer systems

2010

An innovative multiscale (atomistic to mesoscale) model capable of predicting carbon nanotube (CNT) interactions and dispersion in water/surfactant/polymer systems was developed. The model was verified qualitatively with available experimental data in the literature. It can be used to computationally screen potential surfactants, solvents, polymers, and CNT with appropriate diameter and length to obtain improved CNT dispersion in aqueous medium. Thus the model would facilitate the reduction of time and cost required to produce CNT dispersed homogeneous solutions and CNT reinforced materials.CNT dispersion in any water/surfactant/polymer system depends on interactions between CNTs and surrounding molecules. Central to the study was the atomistic scale model which used the atomic structure of the surfactant, solvent, polymer, and CNT. The model was capable of predicting the CNT interactions in terms of potential of mean force (PMF) between CNTs under the influence of surrounding molec...