Diffusion in Polymers

Diffusion of small molecules in polymers is an old topic of significance to a wide variety of industrial processes. In this chapter, various diffusion mechanisms of such a process and the corresponding diffusion coefficients are reviewed. In particular, the Rouse and Zimm models, which are developed based on the concepts of Brownian motion and Langevin dynamics for unentangled polymers, are discussed. The free volume theory is also considered.