Transport Properties in Polymers

From the Authors Introduction Diffusion is one of the few manageable nonequilibrium pro- cesses during which matter is transported through a system. Traditionally, diffusion is studied in physical chemistry; however, the fundamental understanding of diffusion processes is not possible without involving statistical physics. Diffusion in disordered systems, such as in polymers, has sometimes unexpected features, the nature of which has not yet been determined. Since modern technology involves more and more complex materials which rely on a subtle balance of microscopic effects, the understanding of diffusion processes in these materials is of paramount importance from the practical point of view. A renewed interest in the basic principles of diffusion is a direct result of new experimental data. This was a contributing factor in the preparation of this text. In the first chapter, the phenomenological thermodynamic basics of diffusion is reviewed, and the diffusion equation is derived from the principles of irreversible thermodynamics. The basic mathematical apparatus for solving diffusion equations is reviewed in the second chapter. The third chapter deals mainly with the vast amount of experimental data dealing with diffusion in polymers. . . . A reader interested in particular polymeric systems can use the . . . material as a useful introduction. The last chapter contains basic information concerning random walks and their application to the diffusion in disordered systems. The theory of random walks is widely used in polymer physics where it is usually combined with statistical mechanics to formulate various models of polymeric systems. Finally, useful mathematical formulas and references to the original sources of some mathematical methods are [provided] in the appendices. Some physical constants associated with several polymer solvent systems are also presented.