Anisotropic membrane design

In the highly anisotropic membrane environment, one can expect several different correlation times that correspond to the anisotropic membrane environment and/or the nonspheri-cal molecular probe as well as variations that exist along the membrane normal within the bilayer. Furthermore, the molecular motion is often limited by constraints imposed by the ordered surroundings of the probe. Properly designed spectroscopic experiments can, in many cases, extract both mobility and order parameters and can give a comprehensive picture of membrane fluidity. 

Relationship Between Nodular and Rejecting Layers. Nodular formation was conceived by Maler and Scheuerman (14) and was shown to exist in the skin structure of anisotropic cellulose acetate membranes by Schultz and Asunmaa ( ), who ion etched the skin to discover an assembly of close-packed, 188 A in diameter spheres. Resting (15) has identified this kind of micellar structure in dry cellulose ester reverse osmosis membranes, and Panar, et al. (16) has identified their existence in the polyamide derivatives. Our work has shown that nodules exist in most polymeric membranes cast into a nonsolvent bath, where gelation at the interface is caused by initial depletion of solvent, as shown in Case B, which follows restricted Inward contraction of the interfacial zone. This leads to a dispersed phase of micelles within a continuous phase (designated as "polymer-poor phase") composed of a mixture of solvents, coagulant, and a dissolved fraction of the polymer. The formation of such a skin is delineated in the scheme shown in Figure 11. 

The membrane areas needed in these plants are not huge, but the technical challenges are substantial. Defect-free, anisotropic composite ceramic membranes that are 1-5 pm thick, able to operate continuously at 800-1000 °C, nonpoisoning, nonfouling and low-cost are required—not impossible, but difficult. Conceptual designs of the type of reactor required are beginning to appear. 

Liquid crystals are unique molecular materials because of their anisotropic nature and molecular dynamics [1-4]. Over the last three decades, these materials have been developed as advanced materials for electrooptical applications such as display devices. Liquid crystals also have close relationships to biomolecular systems [5]. Cell membranes form dynamic and anisotropic molecular states, which possess liquid-crystalline behavior. Recently, liquid-crystalline complexes of DNAs and liposomes have been considered as potential systems for gene therapy [6]. The design of liquid crystals by using a variety of structures and interactions may lead to wider applicability of mesomorphic materials. 

Internal goods—Discovery (with Srinivasa Sourirajan) and recognition of the importance of membranes with an anisotropic structure ingenious solution of practical engineering problems in the design, cost-effective construction and safe operation of the world s hrst commercial reverse osmosis plant at Coalinga in California. 

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