Molecular diffusion of organic solvents in multicomponent polymer materials

Molecular diffusion of low molecular weight components and impurities is important step in the polymerization process. Molecular transport also affects other polymer applications including; (1) devolatilization, (2) mixing of plasticizers (or other additives), (3) formation of films, coatings, and foams, (4) time-controlled drug delivery, and (5) separation processes. Although diffusion behavior of penetrants in homopolymers has been studied using theories based on free-volume concepts, few studies have been done for more complicated systems (for example, copolymers, and network polymers, etc.). Moreover, limited data on free-volume parameters have restricted our ability to correlate and predict diffusion behavior using free-volume theories.; The objectives of this research are; (1) to study diffusion behavior of organic solvents in multicomponent polymer materials, and (2) to estimate free-volume parameters in the diffusion model developed by Vrentas and Duda. To achieve these goals several studies were conducted; (1) experimentally obtained diffusion coefficients as well as equilibrium solubilities are provided for organic solvents in polyisobutylene (PIB), random poly(p-methylstyrene-co-isobutylene)(PMS-BR), polyethylene-polystyrene IPN (PES-IPN), and in polyethylene (PE), (2) effects of the ratio of monomers in random PMS-BRs on diffusivity and free-volume parameters are studied, (3) diffusion coefficients of the PES-IPN/toluene system are predicted, using the Sax and Ottino diffusion model and a unsteady-state diffusion model developed in this study, from diffusivity data for homopolymer/toluene systems, (4) the order-disorder transition (ODT) of symmetric poly(styrene-b-isoprene)(SI) diblock copolymers are examined by diffusive probe analysis, (5) solvent free-volume parameters are provided from both low temperature viscosity data and variable temperature {dollar}sp{lcub}13{rcub}{lcub}rm C{rcub}{dollar} NMR {dollar}Tsb1{dollar} relaxation measurements, and (6) a correlation for estimating the size of polymer jumping unit in diffusion is modified.