Polymer–nanoparticle interfacial behavior revisited: A molecular dynamics study

Abstract

By tuning the polymer-filler interaction, filler size and filler loading, we use a coarse-grained model-based molecular dynamics simulation to study the polymer-filler interfacial structural (the orientations at the bond, segment and chain length scales, chain size and conformation), dynamic and stress-strain properties. Simulated results indicate that the interfacial region is composed of partial segments of different polymer chains, which is consistent with the experimental results presented by Chen et al. (Macromolecules, 2010, 43, 1076). Moreover, it is found that the interfacial region is within one single chain size (R(g)) range, irrespective of the polymer-filler interaction and the filler size, beyond which the bulk behavior appears. In the interfacial region, the orientation and dynamic behaviors are induced by the interfacial enthalpy, while the size and conformation of polymer chains near the filler are controlled by the configurational entropy. In the case of strong polymer-filler interaction (equivalent to the hydrogen bond), the innerest adsorbed polymer segments still undergo adsorption-desorption process, the transport of chain mass center in the interfacial region exhibits away from the glassy behavior, and no plastic-like yielding point appears in the stress-strain curve, which indicates that although the mobility of interfacial polymer chains is restricted, there exist no "polymer glassy layers" surrounding the filler. In addition, it is evidenced that the filler particle prefers selectively adsorbing the long polymer chains for attractive polymer-filler interaction, validating the experimental explanation of the change of the bound rubber (BR). In short, this work provides important information for further experimental and simulation studies of polymer-nanoparticle interfacial behavior.

Preparation and Structural Characterization of Vulcanized Natural Rubber Nanocomposites Containing Nickel-Zinc Ferrite Nanopowders

“…Moreover, due to the amorphous characteristics of the natural rubber matrix, the nanoparticles are lodged between the polymer chains or in the interstices of the chains. [34][35][36] Figure 5 shows the X-ray diffraction patterns for natural rubber (NR) and nanocomposites with a different concentration between 1 and 10 phr of NZF nanoparticles. can be associated with an increase in semi-crystallinity of the nanocomposite due to the mobility reduction of the interchains and interdominions in the polymeric matrix provided by the presence of nanoparticles.…”

Polymer and spherical nanoparticle diffusion in nanocomposites

“…However, it is worth noting that in the MC study, the nanoparticles are fixed into the simulation cell, thus they are immobile, contributing into the decrease of polymer diffusivity, whereas in our work they are mobile, and not fixed in the simulation cell. In addition the case of repulsive nanoparticles 54,59,85 , the polymer diffusion coefficient initially increases with increasing nanoparticle loading (up to 5%) 54,85 , it reaches a maximum and decreases further to a D/D 0 = 0.8 ratio, at nanoparticle loading (10%). While in the initial dilute nanoparticle loading, the increase of polymer diffusion (in comparison to its bulk value) reflects the repulsive polymer-nanoparticle interaction, at a higher loading (10%) a reduction of the polymer diffusion is observed, due to simply geometrical reasons, and is affected by the presence of tortuous path 85 .…”

“…It is known that the dynamics of spherical particles (colloids) in a fluid can be predicted by the classic continuum Stokes-Einstein relation. For a spherical particle of radius R in a fluid of viscosity η the diffusion coefficient D SE of the particle is given by 59,61 :…”

“…For such of random walk polymers of length N which diffuse in a network of obstacles the center of mass diffusion, 2R, varies as N −2.452 . In a recent study on lattice MC simulations of long polymers in nanocomposites 44,53 a decrease in polymer chain diffusion was observed when the nanoparticles are fixed in the polymer matrix, with radius (R) smaller than polymer radius of gyration, by both geometric (confinement by fillers) 44,53 and energetic (monomer-nanoparticle interaction) effects [53][54][55][56][57][58][59][60] . Nanoparticle diffusion in a medium is predicted theoretically by the Stokes -Einstein formula 61 in a dilute nanoparticle regime.…”

Local and Global Dynamics in Polypropylene Glycol/Silica Composites

“…Simulations can overcome the problem of the behavior of the interfacial material being swamped by that of the bulk, by enabling a focus on only those chains in proximity to the particles [28,29,30,31,32,33]. Simulations suggest that attraction to the particle surface expands the size of the interfacial chains [34], presumably affecting their motion.…”