Diffusion and relaxation in glassy polymer powders: 2. Separation of diffusion and relaxation parameters

Diffusion and Nuclear Relaxation of Solvent in a Crosslinked Polymer

1. Introduction Nuclear proton relaxation has been recently used for the measurements of pore size distribution (1, 2) and permeability (3) in various fully or partially saturated inorganic porous media. These studies generally implies that the proton relaxation inside a pore is an average of bulk and surface contributions; this latter being dependent of the surface to volume ratio. As a conseq...

A Dual Mode, Local Equilibrium Relaxation Model for Small Molecule Diffusion in a Glassy Polymer

FTIR-ATR (Fourier transform infrared-attenuated total reflectance) spectroscopy and a conventional gravimetric sorption balance were used to study the diffusion of acetonitrile from the vapor phase in glassy cellulose acetate (CA). From the gravimetric experiments, the mass uptake kinetics were well described by a simple Fickian model. However, the experimental data from FTIR-ATR spectroscopy, ...

Structural relaxation and conductivity relaxation in glassy ionics

Anomalous relaxation in diffusion - weighted MRI

for the time dependence of the macoscopic magnetisation M(t) of a sample under the influence of an external field H(t) where γ =μ / Ih is the gyromagnetic ratio of the nuclei under consideration with magnetic moment μ and spin I, i, j, and k are the usual triad of unit vectors along the Cartesian axes. The external field has the form H(t) = H0k + H1(t), where H0 is strong and constant while H1 ...

Basic mechanisms of structural relaxation and diffusion in amorphous silicon

The low-temperature dynamics in amorphous silicon occurs through a sequence of discrete, activated events that reorganize the topology of the network. In this review, we present some recent work done to understand better the nature of these events and the associated dynamics in a-Si. Using the activation-relaxation technique (ART), we generated more than 8000 events in a 1000-atom model of a-Si...