Insight into the Dispersion Mechanism of Polymer-Grafted Nanorods in Polymer Nanocomposites: A Molecular Dynamics Simulation Study

Abstract

Coarse-grained molecular dynamics simulations are performed to investigate the dispersion behavior and the underlying dispersion mechanism of polymer-grafted nanorods (NRs) in a polymer matrix. The influences of grafting density, grafted chain length, and the miscibility between grafted chains and matrix chains are systematically analyzed. The simulation results indicate that the dispersion state of grafted NRs is determined primarily by the excluded volume effect of grafted NRs and the interface between grafted chains and matrix chains. It is found that increasing grafting density and/or grafted chain length induces the conformational transition of grafted chains from mushroom to brush, enlarges the excluded volume of grafted NRs, and enhances the brush/matrix interface in the brush regime, resulting in the improvement of the NR dispersion state. By tuning the interaction strength between grafted chains and matrix chains in a wide range, three general categories of NR spatial organization are found: macroscopic phase separation of the NRs and polymer matrix, homogeneous dispersion of the NRs, and "tele-bridging" of the NRs via the matrix chains. The transition from a "wet" to "dry" brush is observed at the strong brush/matrix interaction. In addition, for the polymer brush grafted on the surface of NRs, the dependence of the brush thickness T b on either grafting density Σ or grafted chain length L g is always weaker than that of polymer brush grafted on flat surface or spherical surface, mainly due to the broader range of moving and the less stretching of polymer chains grafted to NRs. The T b scales with Σ and L g as T b ∼ Σ α L g β , where the ratio β/α is a constant equal to 3, independent of the grafted surface. In general, this work offers a deep insight into the dispersion mechanism of grafted NRs and thus is believed to provide some guidance on the design and preparation of high-performance polymer nanocomposites with tailored dispersion of NRs.

Materials by Design for Stiff and Tough Hairy Nanoparticle Assemblies

“…The strength of the interfacial interaction between nanoparticles and the polymer matrix can be tuned by surface functionalization, which has been shown to greatly influence the dispersion state of the nanoparticles and thus the mechanical properties of the conventional engineered nanocomposite. ,− While some effects on modulus and toughness can be observed here as well for aHNPs, when the whole design space is considered, our simulation results indicate that the ε pnp does not have a major influence on the modulus and toughness relative to other input parameters, as shown in Figure c. This observation is mainly due to the presence of covalent bonds between the nanoparticle and the grafted polymer chains, which limits polymer mobility while also preventing NP aggregation readily.…”

Effect of Nanorod Physical Roughness on the Aggregation and Percolation of Nanorods in Polymer Nanocomposites

“…This nonmonotonic behavior of the rough nanoparticles’ dispersion/aggregation with changing monomer diameter is attributed to a competition of the available free volume gain of the polymer at the rough ridges of the nanoparticle and the entropic penalty to enter those rough ridges. Even though many simulation studies have focused on the morphology ,− and dynamics − of nanorods in a polymer melt using coarse-grained models of nanorods with overlapping beads or connected coarse-grained beads, to the best of our knowledge, studies have not demonstrated how varying nanorod roughness resulting from varying extents of overlap in nanorod model beads impacts the phase behavior of nanorods in the polymer melt, which is addressed in this letter.…”

Theoretical Model of Time–Temperature Superposition Principle of the Self‐Healing Kinetics of Supramolecular Polymer Nanocomposites

“…The number of the grafted polymer chains is determined by the grafting density (Σ):where N is the number of grafted chains per each NP (see Table S1, Supporting Information). When mapping the coarse‐grained bead‐spring model adopted in our simulation to real polymers by setting the diameter of the monomer σ = 1 nm, a grafting density of Σ = 0.3 corresponds to 0.298 chains per nm 2 , indicating a relatively dense brush …”

“…When mapping the coarse-grained bead-spring model adopted in our simulation to real polymers by setting the diameter of the monomer σ = 1 nm, a grafting density of Σ = 0.3 corresponds to 0.298 chains per nm 2 , indicating a relatively dense brush. [13] The grafted polymer chains are fully flexible and are represented by a generic bead-spring model, which was developed by Kremer and Grest. [14] Each grafted polymer chain contains 30 beads.…”