Restricted diffusion of linear and star-branched polyisoprenes in porous membranes

The flux of linear and star-branched polyisoprene through microporous membranes was measured in order to determine the role of molecular structure in hindered diffusion. As the radius of the pore approached the hydrodynamic radius of the polymer, the effective diffusion coefficient decreased. The reduction for the star-branched polymers was much larger than for the linear polymers. The magnitude of the decrease did not agree with a theoretical model that combined the pore partition coefficient of random flight chains with the hydrodynamic resistance of hard spheres. However, the data correspond qualitatively with recent results on size exclusion chromatography of branched polymers