Membrane structure and transport

Although there are several sites of first contact between a foreign compound and a biological system, the absorption phase (and also distribution and excretion) necessarily involves the passage across cell membranes whichever site is involved. Therefore, it is important first to consider membrane structure and transport in order to understand the absorption of toxic compounds. 

Figure 2 sketches different length scales on which water of hydration affects membrane structure and transport properties. The bottom picture represents the smallest unit of a membrane that still contains the essential ingredients of the membrane interior clusters of acidic functional groups and water molecules. The electronic structure of acidic groups and polymer side chains determines the kinetics... 

The majority of todays membranes used in microfiitration, dialysis or ultrafiltration and reverse osmosis cire prepared from a homogeneous polymer solution by a technique referred to as phase inversion. Phase inversion can be achieved by solvent evaporation, non-solvent precipitation and thermcd gelation. Phase separation processes can not only be applied to a large number of polymers but also to glasses and metal alloys and the proper selection of the various process parameters leads to different membranes with defined structures and mass transport properties. In this paper the fundamentals of membrane preparation by phase inversion processes and the effect of different preparation parameters on membrane structures and transport properties are discussed, and problems utilizing phase inversion techniques for a large scale production of membranes are specified. 

The diversity of membrane structures and transport mechanisms studied by SECM demonstrates the utility of this technique for studies of membrane transport (61,157,159,161-163). 

Gardner, C. E., P. R. Unwin, and J. V. Macpherson, Correlation of membrane structure and transport activity using combined scanning electrochemical-atomic force microscopy, Electrochem. Commun., Vol. 7, 2005 pp. 612-618. 

Perfluorinated Ion-Exchange Membranes Structural and Transport Properties of 16... 

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