Über ionotrope Gele mit Kapillarstruktur

Thiele, Heinrich; Hallich, Klaus

doi:10.1515/znb-1958-0905

Cited by 17 publications

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“…More than 50 years ago, Thiele discovered that under certain conditions so-called ionotropic gels with hexagonally ordered capillaries can be formed when an aqueous sol of a negatively charged polysaccharide, e.g., an alginate, is brought into contact with a solution of multivalent cations. − The unidirectional diffusion of the cations through the alginate sol causes orientation and densification of the polyelectrolyte chains and induces the generation of capillaries which are oriented parallel to the diffusion direction. It was shown only recently that the origin of these anisotropic structures is a convective process resulting from two opposing diffusion gradients and friction. , This dissipative phenomenon is quite similar to the Rayleigh−Bénard convection, but in contrast to this, the pattern is fixed during the cross-linking of the polyelectrolyte chains by the cations, thus forming anisotropic structured hydrogels.…”

Section: Introductionmentioning

confidence: 99%

New Anisotropic Ceramic Membranes from Chemically Fixed Dissipative Structures

et al. 2006

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The formation of highly ordered capillaries in alginate gels is due to a dissipative convective process resulting from opposing diffusion gradients and friction. Ceramic membranes with an anisotropic pore structure have been gained from this self-organization process by incorporating inorganic particles into the gel matrix, followed by subsequent ion exchange, drying, and sintering. The aim of this study was to overcome existing preparative deficiencies and to optimize the capillary structure and surface properties with respect to specific technical applications. A new method of ion exchange was introduced, and the sintering program was improved to obtain reproducible product quality. By controlling the parameters of the self-organization reaction, the overall porosity of the ceramic membranes was adjusted to selected values between 60% and 83%. Capillary sizes were varied between 8 and 50 microm. Further modification by metal plating, particle coating, or hydrophobization led to an extended spectrum of applicability of the ceramic membranes. For the first time, anisotropic capillary ceramics have been characterized in detail as to their technical use as catalyst supports, filter membranes, or other solid-fluid and solid-gas contact processes.

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Section: Introductionmentioning

confidence: 99%

New Anisotropic Ceramic Membranes from Chemically Fixed Dissipative Structures

et al. 2006

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Physical Studies on Cell Immobilization Using Calcium Alginate Gels

Cheetham

Blunt

Bocke

1979

Biotech & Bioengineering

217

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SummaryColumns of calcium alginate gel pellets have excellent physical properties when used as a cell immobilization support. Columns of pellets were very resistant to compression and abrasion during passage of high concentrations of sucrose at high flow rates, but if the pellets were formed using low alginate and Caz+ concentrations, compression occurred and flow out of the column was reduced and pressure built up. Transfer of sucrose into the pellets was controlled by internal diffusion, the rate of diffusion being increased by reductions in the alginate and Caz+ concentrations used for immobilization and by the presence of entrapped active cells. Some leakage of cells occurred during use especially when cell division of the entrapped cells took place, but leakage could be minimized by using more highly polymerized pellets.Therefore, immobilization conditions can be chosen so as to form strong pellets, possessing high substrate transfer rates and low rates of cell leakage.

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Low‐angle light scattering of ionotropic gels

Bettelheim

1967

J. Polym. Sci. A‐2 Polym. Phys.

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Low‐angle light‐scattering patterns were obtained on ionotropic gels formed by the diffusion of Ca++ into a polygalacturonate sol. Near the sol–gel boundary, diffraction patterns were obtained which indicated organized structures with repeating units of 1100, 250, and 12.5 μ. Microscopic investigations confirmed that at this gel boundary capillaries run parallel to each other and perpendicular to the direction of diffusion. The diameter of capillaries was 12 μ while their length was in the 1000 μ range. Short interconnecting capillaries were about 200–300 μ in length. Inside the gel, in the more highly crosslinked parts, a disorientation occurs during the aging process with the partial disappearance of capillaries. However, at the gel–sol and gel–semipermeable membrane boundaries, the highly organized structures remain even during prolonged aging. The kinetics of the gel formation was also investigated.

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Über ionotrope Gele mit Kapillarstruktur

Cited by 17 publications

References 0 publications

New Anisotropic Ceramic Membranes from Chemically Fixed Dissipative Structures

New Anisotropic Ceramic Membranes from Chemically Fixed Dissipative Structures

Physical Studies on Cell Immobilization Using Calcium Alginate Gels

Low‐angle light scattering of ionotropic gels

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