DETERMINATION OF EQUILIBRIUM AND DIFFUSION COEFFICIENTS IN POLYMERS BY INVERSE GAS CHROMATOGRAPHY TECHNIQUE

Diffusion of small molecules in polymers is of considerable importance and finds application in various polymer synthesis and devolatilization processes in industry. These processes rely heavily on the diffusion and thermodynamic data for the polymer-solvent system. These data are functions of temperature and concentration of solvent in the polymer. The tightening of environmental regulations and stringent safety and health standarts means that diffusion data are crucial to th epolymer industry. Various techniques exist to measure these properties for a given polymer-solvent system. Among them, the most prominent are gravimetric sorption, piezoelectric sorption, inverse gas chromatography, NMR, and light scattering techniques. Of these, the sorption and the IGC techniques are more frequently used because they measure diffusion coefficients at high polymer concentrations. Sorption techniques which measure diffusion at finite concentrations of solvent, but rely on bulk equilibrium and hence are more time intensive. IGC is a very fast, reliable and accurate technique for diffusion coefficient measurements at temperatures well above, near, and below the glass transition temperature of the polymer (Hadj Romdhane et al., 1995; Pawlish et al, 1987, 1988). In these studies, however, diffusion measurements have been limited to the infinitely dilute region, i.e., the region with negligible amount of solvent.

Although an extensive amount of work has been done in the infinite dilute solvent region using IGC, only a few researchers have extended their results beyond this limit and then only to the consideration of partition coefficients. Therefore, the purpose of this work to extend the IGC technique measure diffusion and partition coefficients for polymer-solvent systems at finite concentrations for various temperatures. And also, the glass transition and melting temperatures and crystallinity of the studied polymer will be determined by thermal analysis equipments in our laboratories.