Infusion of polymer into a porous glass bead as studied by space-resolved Jamin interferometry

Jamin interferometry was applied to a porous glass bead in order to observe transient infusion of solvated polymer into the medium after the polymer was added to the surrounding solvent. Analysis of the fringe pattern along the equator of the bead image allowed us to obtain the concentration profile of the polymer at different times during the infusion. It was found that there are some polymer chains that quickly enter the pores and spread throughout the medium. Afterward, the concentration profile slowly approached an equilibrium uniform distribution. When the polymer chain's dimension was smaller than the pore size, the approach was limited by intrapore diffusion of the chains. In contrast, the entrance of polymer chains into the pores near the bead surface was rate-limiting for polymer chains with a dimension larger than the pore size. The rate of entrance increased at higher concentrations. Unlike studies of transport through a porous membrane, space-resolved interferometry of the porous glass has the advantage of being able to distinguish the entrance from the intrapore diffusion.