| 초록 |
There has been a growing interest in the study of porous media which play an important role in many aspects of science and technology. There are various methods to determine the pore size and pore size distribution of porous media, including gas adsorption, microscopic observation, mercury intrusion, DSC thermoporometry, and so on. In this study, the pore size and pore size distribution of ultrafiltration (UF) membranes with different nominal molecular weight limits (NMWL) were characterized by means of both 1H solid-state nuclear magnetic resonance (NMR) cryoporometry and relaxometry. Cryoporometry uses the melting point depression of a liquid in a porous material according to the Gibbs-Thomson equation given by ΔTm=Tm-Tm(d)=4σslTm/ΔHfρsd=k/d. Whereas, relaxometry utilizes the enhanced relaxation of molecules at a pore surface to calculate the pore diameter from Brownstein and Tarr theory as follows; 1/T1=ρ1(S/V) or 1/T2=ρ2(S/V), where ρ is the surface relaxivity. From these techniques, it is found that a spin-echo signal intensity from a 90°-τ-180° pulse sequence, the inverse longitudinal and transverse relaxation rates (1/T1 and 1/T2) are directly related to the volume of liquid with diameter d confined within the UF membranes. The results showed a good linear correlation between NMWL of UF membranes and the mean pore size measured by both NMR cryoporometry and relaxometry. Estimated pore diameters from these two methods were in good accordance with each other, which was also confirmed by microscopic observation method and solute transport method. |
