Filler-induced composition waves in phase-separating polymer blends

Abstract

The influence of immobile filler particles (spheres, fibers, platelets) on polymer-blend phase separation is investigated computationally using a generalization of the Cahn-Hilliard-Cook (CHC) model. Simulation shows that the selective affinity of one of the polymers for the filler surface leads to the development of concentration waves about the filler particles at an early stage of phase separation in near critical composition blends. These "target" patterns are overtaken in late-stage phase separation by a growing "background" spinodal pattern characteristic of blends without filler particles. The linearized CHC model is used to estimate the number of composition oscillations emanating from isolated filler particles. In far-off-critical composition blends, an "encapsulation layer" grows at the surface of the filler rather than a target pattern. The results of these simulations compare favorably with experiments on filled phase-separating ultrathin blend films in which the filler particles are immobilized on a solid substrate.

Modeling the Dynamic Behavior of Diblock Copolymer/Particle Composites

“…L 2 N x + N y (9) R(t) ) (1 + Φ)(γ + RΦ) -1/3 G(At(γ + RΦ)) (10) and thereby modify the structure of the system. We present three snapshots of this system in Figure 4 for the early (Figure 4a), intermediate (Figure 4b), and late ( Figure 4c) stages of the microphase separation.…”

Simulations of Filled Polymers on Multiple Length Scales

“…In the first study, we use molecular dynamics (MD) simulations [6] to explore the effect of a single nanoscopic, model filler particle on the structure, dynamics, and glass transition temperature of a model polymer melt [7]. In the second study, we use time-dependent Ginzburg-Landau (TDGL) methods [8] to study the effect of model nanometer to micron-sized fillers on the mesoscale structure of phase-separating polymer blends [9]. In the third study, we use the finite element method [10] in a preliminary study to probe the effect of fillers on the mechanical properties of filled blend microstructures [11].…”

Electric-field induced alignment of nanoparticle-coated channels in thin-film polymer membranes

“…For example, dissipative particle dynamics have been used by Hore and Laradji [13][14][15][16] and a) Electronic mail: pmillett@uark.edu others 17 to study various particle assemblies in binary phaseseparating mixtures. Hybrid models, on the other hand, represent a different approach, in which the fluid or polymer phase is represented by concentration or density fields on a discrete mesh, while the dispersed particles evolve in continuous space by discrete moves informed by their instantaneous force or energy, the earliest example from Kawakatsu et al 18 With regards to particles in phase-separating mixtures, hybrid models have utilized the Lattice Boltzmann method 8 to represent low-viscous fluids, as well as Cahn-Hilliard (CH) [18][19][20][21][22] and Self-Consistent Field 23 theories to represent viscous polymer melts. A good review of these approaches, and their application to polymer nanocomposites, can be found in the recent literature.…”