Diffusion of nonadsorbing polymers within hierarchically structured colloidal aggregates

Nonadsorbing polystyrene is used to examine the diffusivity of large molecu les within hierarchically structured ceramic particles, containing an inter connected network of macropores permeating an interconnected network of sma ller pores. A theory developed to describe solvent diffusion within ordered arrays of polymer spheres is applied to understand the diffusion of nonads orbing polystyrene within hierarchically structured particles as measured b y pulsed-field gradient NMR. The model captures an important feature of the data-diffusivity within the particles will be most significantly reduced f or a molecule of intermediate size due to the interplay of partitioning and diffusion within the network of smaller pores. While the measured values d iffer from those predicted by the model, the differences are attributed to assumptions made in describing diffusion and partitioning within the microp articles. (C) 2000 Academic Press.