Interfacial thermal transport and structural preferences in carbon nanotube–polyamide-6,6 nanocomposites: how important are chemical functionalization effects?

Abstract

We employ reverse nonequilibrium molecular dynamics simulations to investigate the interfacial heat transfer in composites formed by an ungrafted or a grafted carbon nanotube which is surrounded by oligomeric polyamide-6,6 chains. The structural properties of the polymer matrix and the grafted chains are also studied. The influence of the grafting density, the length of the grafted chains as well as their chemical composition on the interfacial thermal conductivity (λi) are in the focus of our computational study. For the considered grafted polyethylene and polyamide chains we do not find a sizeable difference in the observed λi values. In contrast to this insensitivity, we predict a rather strong influence on λi by the grafting density and the length of the grafted chains. This dependence is an outcome of modifications in the structural properties of the polymer matrix as well as the grafted chains. Functionalization of the nanotube has a sizeable influence on the interfacial thermal conductivity. Its enhancement is caused by the chemical bonds between the nanotube and grafted chain atoms which reduce the number of Kapitza resistances hindering the heat transfer in polymer samples. The phonon density of states profiles confined to the bonded nanotube and the grafted chain atoms are used to emphasize the phonon support of the thermal conductivity in nanocomposites with grafted tubes. Strategies to tailor nanotube containing composites with higher thermal conductivities than that realized in the bare polymer are shortly touched.

Structure and thermodynamics of grafted silica/polystyrene dilute nanocomposites investigated through self-consistent field theory

“…It is stressed at this point that the density profiles obtained from our SCFT/SL + SGT model are closer to the corresponding ones obtained from atomistic molecular dynamics simulations 21,[76][77][78] than FOMC. If one averages out the oscillations of the atomistic density profiles, then their smeared analogues come out very close to the density profiles of SCFT/SL + SGT (and especially close to HFD) in terms of the position of the peak and the width of the depletion zone near the solid surface.…”

A review of the interfacial characteristics of polymer nanocomposites containing carbon nanotubes

“…The optimization of the interface is another effective way to improve the thermal properties of polymer nanocomposite materials containing carbon nanotubes. [388][389][390] The interface between the carbon nanotube and the surrounding polymer matrix can cause a large thermal resistance, and this is the primary factor of affecting the heat ow in polymer nanocomposite materials. [391][392][393][394] To achieve excellent thermal properties of these polymer nanocomposite materials, it is crucial to improve the rate of heat transfer across the interface by modulating the interaction between the two components.…”

Molecular dynamics simulations of flame propagation along a monopropellant PETN coupled with multi-walled carbon nanotubes

“…Zahedi et al 56 and Alaghemandi et al 57 In the RNEMD approach, a constant heat flux is imposed on the simulation box by performing velocity exchanges between the coldest particle (from the hot layer) and the hottest particle (from the cold layer) in a given direction. If the masses of the particles being exchanged are different, then an exchange of velocities relative to the center of mass motion of the two atoms is performed, to conserve the total kinetic energy of the system.…”

“…Zahedi et al 56 investigated the structural properties of the polymer matrix around the CNTs. A highly ordered polymer matrix structure was observed in the interphase region as quantified using the normalized density profiles around the CNTs.…”