PORE-SIZE DISTRIBUTION MEASUREMENTS OF POLY(METHYL METHACRYLATE) HYDROGEL MEMBRANES FOR ARTIFICIAL-KIDNEYS USING DIFFERENTIAL SCANNING CALORIMETRY

The freezing and melting behavior of water in 15 types of poly (methyl methacrylate) (PMMA) hydrogel-hollow-fiber membranes utilized in arti ficial kidneys for ordinary hemodialysis, high flux hemodialysis, hemo filtration, and protein permeable hemofiltration, etc., was investigat ed using a differential scanning calorimeter, The freezing and melting temperatures of freezable water in the PMMA hydrogels were lower than those of bulk water, although the freezable water had almost the same mobility as that of bulk water, indicating that the freezable water w as assigned to free water confined in the pores, i.e., freezable pore water, Pore size distribution curves regarding the PMMA membranes were then calculated from the melting endotherms and the freezing exotherm s of the pore water via thermoporosimetry. The average pore radii of t he membranes were also calculated from the pore size distribution curv es, and they were found to be in good theoretical agreement with the a verage pore radii obtained from the water permeability, The number of pores was also found to correlate with the number obtained from the wa ter permeability. (C) 1995 Academic Press, Inc.