WATER SWELLABLE

The development of water-swellable polymers depends on aspects of their synthesis, properties evaluation, optimization and correlation of these properties with synthesis conditions. Obviously, studying the behavior of SAH in contact with liquid and solid phases of the soil as well as with plants requires developing physical models and algorithms suitable for the prediction of SAH efficiency. 

This subject can be considered in terms of five different types of molecules or materials (a) biologically inert, water-insoluble polymers (b) water-insoluble polymers that bear biologically active surface groups (c) water-swellable polymeric gels, or amphiphilic polymers that function as membranes (d) water-insoluble but bioerodable polymers that erode in aqueous media with concurrent release of a linked or entrapped bioactive molecule and (e) water-soluble polymers that bear bioactive agents as side groups. 

Zweigle, M.L. and Lamphere, J.C. "Crosslinked, Water-Swellable Polymer Microgels," US Patent 4,172,066(1979). 

Several approaches have been undertaken to construct redox active polymermodified electrodes containing such rhodium complexes as mediators. Beley [70] and Cosnier [71] used the electropolymerization of pyrrole-linked rhodium complexes for their fixation at the electrode surface. An effective system for the formation of 1,4-NADH from NAD+ applied a poly-Rh(terpy-py)2 + (terpy = terpyridine py = pyrrole) modified reticulated vitreous carbon electrode [70]. In the presence of liver alcohol dehydrogenase as production enzyme, cyclohexanone was transformed to cyclohexanol with a turnover number of 113 in 31 h. However, the current efficiency was rather small. The films which are obtained by electropolymerization of the pyrrole-linked rhodium complexes do not swell. Therefore, the reaction between the substrate, for example NAD+, and the reduced redox catalyst mostly takes place at the film/solution interface. To obtain a water-swellable film, which allows the easy penetration of the substrate into the film and thus renders the reaction layer larger, we used a different approach. Water-soluble copolymers of substituted vinylbipyridine rhodium complexes with N-vinylpyrrolidone, like 11 and 12, were synthesized chemically and then fixed to the surface of a graphite electrode by /-irradiation. The polymer films obtained swell very well in aqueous... 

This study is similar to those previously done by Derbyshire and Duff (20) and Nystrom et al. (21) who studied water swellable gels. However, in the first of these, the use of proton NMR complicated the relaxation data because of proton-proton coupling. Furthermore, their study focused on the freezing (or non-freezing) of water which also complicated matters. In the present study, we are always well above the freezing point of toluene so that one need not worry about the freezing of the solvent. The study by Nystrom et al. (21) used deuterium NMR of D2O, but an unusual temperature dependence was observed, possibly due to the exchange of the protons or deuterons. Our present data are not complicated... 

Another very interesting class of crosslinked polyelectrolytes are the so-called superabsorbents. They predominantly consist of crosslinked and (partially) neutralized poly(acrylic acid) and, hence, represent a network of flexible polymer chains that carry dissociated, ionic groups. Due to this structure they can function as water-swellable gels. Although they are hard, sandy powders in a dry... 

An intermediate layer acting as a control element, which separates the drag layers. This control element, made from a mixture of water-swellable polymers, would act as a barrier in order to delay the release of the dose of the drag present in the second layer. 

Operating as described, cylindrical three-layer tablets were prepared, weighing about 900 mg and having two layers of active substance separated by a barrier layer of water swellable polymer mixture (granulate B). 

Granular Cold-Water-Swellable (CWS) and Cold-Water-Soluble... 

The implant consists of a water-swellable Hydron (cross-linked ethylene glycomethacrylate) polymer matrix in which estradiol valerate (Norgestomet) crystals are dispersed. It is used for the synchronization of estrus/ovulation in cycling heifers. Once implanted in the animal s ear, the implant delivers estradiol valerate at the rate of 504 ug cm-2 day-172 over a period of 16 days. 

Gums. Gums are hydrophobic or hydrophilic polysaccharides derived from plants or microorganisms that upon dispersing in either hot or cold water produce viscous mixtures or solutions (i.e., gels (1)). As used in the modern sense, the term gum includes any water-soluble or water-swellable polysaccharide or its derivative. This includes starch and dextrins and various derivatives of cellulose. The latter, however, are considered separately. 

Superabsorbents. Water-swellable polymers are used extensively in consumer articles and for industrial applications. Most of these polymers are cross-linked acrylic copolymers of metal salts of acrylic acid and acrylamide or other monomers such as 2-acrylamido-2-methylpropanesulfonic acid. These hydrogel forming systems can have high gel strength as measured by the shear modulus (134). Sometimes inorganic water-insoluble powder is blended with the polymer to increase gel strength (135). Patents describe processes for making cross-linked polyurethane foams which contain superabsorbent polymers (136,137). 

Eudragit NE 30 D Aqueous dispersion 30% Water Swellable, permeable Sustained release, tablet... 

In addition to this, superabsorbent polymers are used as additives in fire extinguishing water, materials for water-swellable toys, paint for prevention of water leakage, for removal of water in oil, etc. 

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