APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014;
Denver, Colorado
Session Y14: Invited Session: Dynamics of Polymer Nanocomposites
8:00 AM–11:00 AM,
Friday, March 7, 2014
Room: 301-303
Sponsoring
Units:
DPOLY DBIO
Chair: Russell Composto, University of Pennsylvania
Abstract ID: BAPS.2014.MAR.Y14.3
Abstract: Y14.00003 : Microscopic Theories of Diffusion, Tube Localization and Slow Relaxation in Polymer Nanocomposites
9:12 AM–9:48 AM
Preview Abstract
Abstract
Author:
Kenneth Schweizer
(University of Illinois, Urbana-Champaign)
Dynamics in polymer nanocomposites is rich and complex but poorly understood
due to the presence of multiple length scales, excluded volume effects and
other factors. We have developed new statistical mechanical theories at the
level of forces for particle and polymer motion in flexible and rigid
polymers. This talk presents an overview, including quantitative comparisons
to simulations and experiments. First, by combining Brownian motion, polymer
physics and mode coupling ideas, a self-consistent theory for the
non-hydrodynamic diffusion of a spherical nanoparticle in melts has been
constructed. Three competing mechanisms are predicted: sieving-like
diffusion through unentangled regions, reptation-driven constraint release
in entangled melts, and activated hopping through entanglement meshes. The
controlling mechanism depends on particle size, tube diameter and
entanglement density. The approach can also treat soft fillers, nonspherical
particles, adsorption, solutions and networks. Second, a self-consistent
microscopic theory for the slow dynamics of a needle fluid in a matrix of
static spheres has been developed which exactly enforces inter-needle
topological uncrossability and needle- sphere impenetrability constraints at
the two-body level. The rich dependences of the effective tube diameter and
anisotropic diffusion constants on filler-needle aspect ratio, polymer
concentration and particle volume fraction has been established. Due to
steric blocking of longitudinal motion by obstacles, a literal localization
transition is predicted that is controlled by the particle to tube diameter
ratio. For a restricted window of parameter space, needles are predicted to
diffuse via a ``renormalized'' reptation dynamics where compression of the
tube and suppression of longitudinal diffusivity enter in a manner that
depends on all system variables. Generalization of the approach to treat
mobile fillers, flexible chains and nonrandom microstructure is possible.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.MAR.Y14.3