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The line-width of the nuclear magnetic resonance (NMR) signal gets narrow, in general, with an increase in the temperature. In contrast, the NMR line-width of the water proton in agarose gels was found to increase with an increase in the temperature up to about 30°C. As for the other polysaccharide gels, such as curdlan-type polysaccharide, and κ-and λ-carrageenan gels, the NMR line-width of water increases with an increase in the temperature. The anomalous temperature dependence of the line-width was most marked in agarose gels than in other polysaccharide gels. The close relationship between the gel network, which consists of small cavities (microspace) of the micelle, and the magnitude of the anomality was revealed, this anomalous effect was named the “Micro-Space Effect.”

Electrochemical and dilatometric studies have indicated that at least three states of water exist in macromolecular gels. The properties of each state of water in gels such as agarose gels were investigated by highresolution and broadline PMR over the temperature range from +50 to −60°C. The linewidth of water protons in gels was found to depend markedly on the water content of gels, and the linewidth vs. water content curve gave two inflection points. One of the inflection points can be attributed to the so-called bound water, but the other cannot be explained unless three states of water are assumed in gels. Three kinds of transition temperatures were confirmed by anomalous changes in the PMR linewidth below 0°C. The so-called bound water exhibited no transition temperature between 0 and −20°C, and free water gave the transition temperature at 0°C. Moreover, the transition temperature of a quantity of water was distributed in the range from 0 to −20°C. On the basis of the transition temperature, the properties of water in macromolecular gels are discussed.

The relationship between the rheological properties and the states of water in macromolecular gels is investigated by both the rheological and nuclear magnetic resonance methods. In accordance with the stress-strain curve, macromolecular gels are shown to be classifiable into: (1) an agarose type of gel which shows great gel strength and brittleness at breaking; (2) a κ-carrageenan type of gel showing great gel strength, but ductility at breaking, and (3) a λ-carrageenan type of gel, which has very little gel strength and is pasty. The dependence of the NMR line-width of water in gels on the polymer concentration and on the temperature reveals that the motional state of water in gels is restricted in this order: the agarose type of gel>the κ-carrageenan type of gel>the λ-carrageenan type of gel. These results show that the state of water is closely related with the rheological properties of macromolecular gels.

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Die NMR‐Linienbreite der Wasserprotonen nimmt mit steigender Temperatur bis zu 30°C zu.

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