Characterizing Porous Materials

While many porous materials comprise inorganic structures that are resistant to shrinking, many polymeric porous materials lose their porous structure when water is removed from their pores (just like a sponge undergoes shrinking upon evaporation). Such materials are called meta-stable porous materials. They present a challenge for typical characterization techniques, which only interrogate dried solid materials. Dr. Allgeier uses a technique known as low-field nuclear magnetic resonance (LF NMR). He gained this specialized expertise during his prior employment with DuPont Chemical Company.  Hydrogels are important examples of meta-stable porous materials and are employed in a number of biomedical applications from contact lenses to drug delivery and wound care.  The performance of hydrogels are dependent upon their porosity, e.g. in drug delivery reduced pore sizes can restrict the rate of drug diffusion into the body.

Students will learn how to use various instruments, including the LF-NMR to detect differences in hydrogel porosity and X-ray micro-computed tomography (XµCT).  Since XµCT relies on density contrast in imaging and hydrogels have high permeability, the density of the aqueous phase may be increased with added iodide salts.  A comparison of XµCT and LF-NMR data from wetted porous media and electron microscopy images of lyophilized (dried) samples will be constructed and considered in light of mechanical and transport (e.g. drug release) properties of hydrogel samples to define the utility of the various analytical methods.