硫酸化アルギン酸電解質膜の圧力こう配による溶媒透過挙動

概要

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We have investigated the flow rate of methanol aqueous solutions through alginate sulfate (AS) electrolyte membranes under a constant pressure gradient. The solvent flow rate for the AS membranes with low cross-linking densities is considerably higher than that of alginic acid membrane when the methanol fraction (φ) is low. The solvent flow rate drastically decreases as φ increases, and no solvent permeation is observed when φ > 0.6. This strong φ dependence of flow rate is not simply explained by the φ dependence of swelling degree (Θ), because the reduction in Θ by increasing φ is considerably small. The confocal microscopy reveals a higher order network structure with a mesh size of ca. 10μm in the water-swollen AS membrane. The network structure results from the phase separation of the hydrophilic and hydrophobic domains. The hydrophilic and hydrophobic domains are mainly composed of the sulfated blocks and non-sulfated blocks, respectively. The mesh size of the network structure becomes considerably smaller as φ increases. The solvent permeability of the AS membranes is mainly controlled by the mesh size of the higher order network structure.