Diffusion of Penetrants in Polymers

摘要

Much effort has been expended in trying to understand and predict the unusualphenomena which can occur when initially glassy polymers are exposed to small-molecule gases, organic vapors or liquids. Sorption of the gas or vapor seems to occur at two distinctly different sorption sites (dual mode sorption), and influx of the penetrant leads to a non-Fickian front traveling at constant velocity (case-II diffusion). Because traditional measurement techniques such as sorption and permeation are complicated by these very phenomena which they try to explain, attempts to determine to what extent these phenomena are governed by diffusive characteristics of glassy transport rather than by the interplay of diffusion and polymer relaxation have been frustrated. Instead, a method of observing diffusion which does not require penetrant transport across a surface and influx into the sample must be used. Keywords: Glassy polymers, Self-diffusion, Probe dye molecule, Vrentas-Duda free volume theory, Penetrants, Materials, Holographic Relaxation Spectroscopy(HRS), Polystyrene, Toluenes, DD1473. (JG)