Diffusion of nonadsorbing polymers within hierarchically structured colloidal aggregates

Nonadsorbing polystyrene is used to examine the diffusivity of large molecules within hierarchically structured ceramic particles, containing an interconnected network of macropores permeating an interconnected network of smaller pores. A theory developed to describe solvent diffusion within ordered arrays of polymer spheres is applied to understand the diffusion of nonadsorbing polystyrene within hierarchically structured particles as measured by pulsed-field gradient NMR. The model captures an important feature of the data-diffusivity within the particles will be most significantly reduced for a molecule of intermediate size due to the interplay of partitioning and diffusion within the network of smaller pores. While the measured values differ from those predicted by the model, the differences are attributed to assumptions made in describing diffusion and partitioning within the microparticles. (C) 2000 Academic Press.