Sorption and swelling in ultra-thin polymer films

Different polymers were investigated with respect to the sorption of solven ts and gases. Depending on the chemical nature of the polymers this sorptio n leads to polymer swelling. The degree of swelling D/D-0 was measured util izing Small angle X-ray scattering (SAXS) as well as Surface plasmon resona nce (SPR). From the change in film thickness after swelling in different so lvents Hildebrand parameters of the polymers were determined. By crosslinki ng of the polymer films the degree of swelling can be controlled. In the ca se of ultra-thin polyimide films a higher degree of crosslinking led to a d ecreased selectivity of the transport of gases through the membrane. Reptat ion of macromolecules was also investigated and the influence of polymer sw elling in different solvents has a great influence on the selectivity and d iffusion coefficient.