Development of methods for quantitative characterization of network morphology in pharmaceutical hydrogels.

We have employed a variety of methods which satisfactorily characterize the structure of polymeric hydrogels beyond the level of information provided by a single swelling test. We applied these techniques to gels which have potential for use as pharmaceuticals for the control of elevated phosphorous levels in patients suffering from chronic kidney failure. These 'fingerprinting' techniques help us understand the effects of various processing parameters on the gel morphology. Wide-angle X-ray diffraction experiments verified the structure and reproducibility across synthesized hydrogel batches. Measurements of the temperature- and frequency-dependent dielectric relaxation provided information on the network topology. Real-time diffusion experiments were performed using inductively coupled plasma atomic emission spectroscopy. Spherical gel particles (510 microns diameter) were used to measure equilibrium phosphate loadings of 4.5 mmoles g-1 from direct measurement of the decrease in phosphate ion concentration in aqueous solutions.