Computational Study of Nanoparticle Dispersion and Spatial Distribution in Polymer Matrix under Oscillatory Shear Flow

Abstract

In this work, nonequilibrium molecular dynamics simulations were performed to investigate the dispersion and spatial distribution of spherical nanoparticles (NPs) in polymer matrix under oscillatory shear flow. We systematically analyzed the influences of four important factors that consist of NP-polymer interfacial strength, volume fraction of NPs, shear conditions, and polymer chain length. The simulation results showed that the oscillatory shear can greatly improve the dispersion of NPs, especially for the polymer nanocomposites (PNCs) with high NP-polymer interfacial strength. Under specific shear conditions, the NPs can exhibit three different spatial distribution states with increasing the NP-polymer interfacial strength. Interestingly, at high interfacial strength, we observed that the NPs can be distributed on several layers in the polymer matrix, forming the PNCs with sandwich-like structures. Such well-ordered nanocomposites can exhibit a higher tensile strength than those with the NPs dispersed randomly. It may be expected that the information derived in present study provides a useful foundation for guiding the design and preparation of high-performance PNCs.

How the flow affects the phase behaviour and microstructure of polymer nanocomposites

“…In other words, imposing a flow field allows for a wider range of   0 , g Ra to lie within the miscible region, in line with previous research. 7,[22][23][24][25] According to our model, therefore, flow allows for a better dispersion of spherical fillers in PNCs.…”

“…by choosing a system with favourable hydrogen bonding interactions like a poly(2-vinylpyridine)/silica system 20 or by chain grafting to gain from the favourable interactions between grafted chains and polymer matrix. 5,6,11,21 However, surface modification can lead to loss of material properties, 22 and for this reason the application of mechanical stresses (which have been shown to assist in breaking up NP aggregates allowing for better NP dispersion 7,[22][23][24][25] ) is usually preferred. A common process is melt-blending by shear, a very attractive approach both from an economic and an environmental point of view (since solvents are not required during processing 26 ) producing nanocomposites with highly dispersed NPs.…”

“…That shear can help increase the dispersion of spherical NPs within polymer matrices is also supported by simulations. 16,22,23 In the literature, shear has been quite often reported to induce changes 27,28 in the solubility of polymers both in solutions and blends. [29][30][31] Rangel-Nafaile et al 32 found that the cloud point shifts towards higher temperatures with shear stress, an effect which they described thermodynamically by considering the total free energy to be the sum of the Flory-Huggins free energy of mixing (assumed not to be affected by the flow) and the free energy due to deformation of polymer coils from the flow using an expression proposed by Marrucci 33 for Hookean dumbbells (see Ch.…”

Molecular simulation study of role of polymer–particle interactions in the strain-dependent viscoelasticity of elastomers (Payne effect)

“…Following previous work, 31 the standard bead-spring model proposed by Kremer and Grest 32 was adopted to represent the polymer chain in the simulations. In this model, each bond would correspond to n = 3-6 covalent bonds along the backbone of a realistic chemical chain when mapping the coarse-grained model to a real polymer.…”

Tailoring the alignment of string-like nanoparticle assemblies in a functionalized polymer matrix via steady shear

“…For these reasons, coarse-grained models which group atoms or molecules into single particles have been widely adopted to investigate the sheared PNC systems. [40][41][42][43][44][45][46][47][48][49][50][51][52] Although these models are of much lower resolution than atomistic, they still can describe the microscopic nature of the systems at length scales comparable to the intermolecular distances. However, up to now, there still no study related to the investigation of functionalized polymer/NP systems under shear.…”