Mechanisms of reinforcement in polymer nanocomposites

Abstract

Coarse-grained molecular dynamics simulations are used to elucidate molecular mechanisms responsible for different mechanical behaviours of elastomers containing spherical particles with different volume fractions. We observe that different filler volume fractions result in qualitatively different responses of the polymer nanocomposite to tensile strain. At relatively low filler volume fraction a yield drop appears in the stress-strain curve. As the filler volume fraction increases there is a reduction in the rate of plastic hardening, becoming plastic softening at sufficiently high filler volume fraction. We demonstrate that these behaviours are a result of the network formed by the polymer chains and filler particles. We identify three distinct molecular structural motifs between polymer and filler particles whose relative prevalence varies with the filler volume fraction and as the system is dynamically strained. We show how this evolution in molecular structure is directly linked to the observed mechanical response.

Transport anomalies emerging from strong correlation in ionic liquid electrolytes

“…To further help answering the above questions, we adopt a modified version of the persistence measure defined in an earlier work. 45 The persistence is defined as the fraction of oxygen atoms coordinating a sodium at time t that remains the same as at time t = 0. In other words, if the persistence is equal to one then the exact same oxygen atoms from t = 0 are coordinating the Na + cations at t = t. If the persistence is equal to zero then a completely different set of oxygen atoms is coordinating the Na + .…”

Tailoring the mechanical properties of polymer nanocomposites via interfacial engineering

“…[18][19][20][21][22] However, it is extremely difficult to produce well-dispersed states of immiscible inorganic NPs in a polymer matrix. At the same time, a good NP dispersion has been shown 23 to be responsible for good mechanical reinforcement. Various strategies have been suggested for the control of the spatial distribution of NPs, invoking their surface modification such as by adding surfactants (cationic, anionic or nonionic), [24][25][26] inorganic surface modification, 27,28 adsorbent modification, 29,30 and using grafted polymer chains.…”

A Coarse-Grained Force Field for Silica–Polybutadiene Interfaces and Nanocomposites

“…These system sizes are impressive by current standards, but they still fall short of those required to model the hierarchical organization of the nanoparticles into fractal-like structures, such as those which characterize many rubber nanocomposites [ 33 ]. Thus, most simulations of PNCs are still carried out with coarse-grained (CG) models, typically based on bead-and-spring polymer chains and Lennard–Jones-type (LJ) interaction potentials [ 34 , 35 , 36 , 37 , 38 , 39 ] or some appropriate generalization of them [ 40 ]. An even coarser description is the one based on Dissipative Particle Dynamics (DPD) [ 41 , 42 ].…”