Nanoparticle Dispersion and Aggregation in Polymer Nanocomposites: Insights from Molecular Dynamics Simulation

Abstract

It is a great challenge to fully understand the microscopic dispersion and aggregation of nanoparticles (NPs) in polymer nanocomposites (PNCs) through experimental techniques. Here, coarse-grained molecular dynamics is adopted to study the dispersion and aggregation mechanisms of spherical NPs in polymer melts. By tuning the polymer-filler interaction in a wide range at both low and high filler loadings, we qualitatively sketch the phase behavior of the PNCs and structural spatial organization of the fillers mediated by the polymers, which emphasize that a homogeneous filler dispersion exists just at the intermediate interfacial interaction, in contrast with traditional viewpoints. The conclusion is in good agreement with the theoretically predicted results from Schweizer et al. Besides, to mimick the experimental coarsening process of NPs in polymer matrixes (ACS Nano 2008, 2, 1305), by grafting polymer chains on the filler surface, we obtain a good filler dispersion with a large interparticle distance. Considering the PNC system without the presence of chemical bonding between the NPs and the grafted polymer chains, the resulting good dispersion state is further used to investigate the effects of the temperature, polymer-filler interaction, and filler size on the filler aggregation process. It is found that the coarsening or aggregation process of the NPs is sensitive to the temperature, and the aggregation extent reaches the minimum in the case of moderate polymer-filler interaction, because in this case a good dispersion is obtained. That is to say, once the filler achieves a good dispersion in a polymer matrix, the properties of the PNCs will be improved significantly, because the coarsening process of the NPs will be delayed and the aging of the PNCs will be slowed.

Influence of nanoparticle size, loading, and shape on the mechanical properties of polymer nanocomposites

“…[16][17][18][19][20][21][22][23][24][25][26] Concerning the nanofiller size and shape, computational studies have focused on fillers whose size is comparable to the characteristic length scales of the polymer matrix, namely the radius of gyration of the polymers or the size of their monomers. 21 mal NP dispersion and strong polymer-NP interactions 27 have shown that the smaller NPs have better reinforcing properties, leading to tougher PNCs. 17,19,28 Furthermore, the increase in the aspect ratio of the nanoparticles, that finds an experimental correspondence in carbon nanotubes 10,29 or clay sheets, 10 has been observed to lead to an increase of the mechanical reinforcement of PNC.…”

Correlations between mechanical, structural, and dynamical properties of polymer nanocomposites

“…We model the PNC in a regime of strong polymer-filler interactions and optimal degree of dispersion [18]. Fillers are small if compared to the radius of gyration of the chains.…”

Effect of Thermal-Electric Cross Coupling on Heat Transport in Nanofluids

“…Consequently, it is reasonable to apply the theory of molecular dynamics to the nanoparticle system and thus the thermal motion of nanoparticles is equivalent to the thermal motion of macromolecules, which is accepted in many literatures [49][50][51][52]. In the following, we will adopt the vibration movement of the nanoparticle, denoted in Figure 1b, representing the complicated thermal motion to show the effect of the thermal-electric cross coupling on heat transport in nanofluids.…”