Quasi-equilibrium gradient structures in glassy polymer-plasticizer systems

The kinetic regularities of the formation of diffusion zones in glassy poly mers with a limited source of diffusant were studied by electron microprobe X-ray analysis and optical interferometry for systems based on nitrocellul ose, polystyrene, and a number of plasticizers. The growth of these zones w as shown to be described by either the diffusion-controlled kinetics or the kinetics controlled by the relaxation processes, depending on the remotene ss of the process temperature from the glass transition temperature of a po lymeric matrix. As the average diffusant concentration in a zone approaches a concentration corresponding to glass transition, the growth of the diffu sion zones is markedly retarded, due to the concentration dependence of the diffusion coefficients. Quasi-equilibrium gradient zones retaining their s tructure for a long time can be formed in polymeric systems because of the transition of solutions to a glassy state.