Porous structure of membranes of an acrylonitrile copolymer. Porosity, H-1-NMR permeability

Nanoporous polymer membranes (porosity phi approximate to 0.7) used fur dia lysis are studied fi om NMR relaxation times of water confined in the pore space. Fast interpore mater diffusion is observed. True structural paramete rs are evidenced: i) a reduced NMR relaxation time; tau, which reflects the width of the pore-size distribution; ii) the average polymer-grain size of the solid matrix deduced from NMR experiments performed oil membranes part ially filled by water. A relation is found between the ratio k/tau (2), whe re k is the permeability to water and the porosity. This relation is in qua litative agreement with numerical simulations reported in the literature on low-porosity systems and with experimental results obtained for sedimentar y rocks and for fused glass model systems. It supports the idea that tau is the relevant. structural parameter to describe convective transport in a w ide class of porous systems.