Superabsorbent polymer is well known to be capable of absorbing thousands of times its weight of water. Superabsorbent polymer gel is used here to exhibit a convection current of water by heating because with its high absorbent property the gel's density is almost equal to that of water. However, for good demonstration of the experiment it is necessary to use a colored polymer gel that is optimally cross-linked. The synthesis of colored polyacrylic acids for use as a new teaching material is described here. After evaluating several pigments to color the polymer acid, we found commercial polyacrylic pigment (Mr. Color [oily] from Gunze Co. Ltd.) and safranin O to be the most suitable color agents for these experiments.
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Takaki, Morio; Itoh, Toshiyuki. J. Chem. Educ.1999 76 62.
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