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It is important for montmorillonite (Mt) -based nanocomposites to achieve good intercalation or exfoliation of Mt in composite structure. In this paper, N-[3-(dimethylamino)propyl] methacrylamide (DMAPMA), which is nonionic in neutral solution but cationic character in acid solution, and acrylic acid (AA) were used to modify Mt with AA together. Here DMAPMA and AA were used not only as the intercalators to disperse and intercalate Mt but also as the main monomers to form amphoteric nanocomposite hydrogels. The XRD and TEM results illustrated that an exfoliated or a highly intercalated nanocomposite structure was obtained. Compression strength of amphoteric nanocomposite hydrogel reached 54.4 kPa under the water content of 99.8%. It should be emphasized that the excellent mechanical property of the hydrogels was reached without adding chemical crosslinking agents. Compared with the organic hydrogel, the hydrogels showed significant improvement in swelling capacity.

The poor stability of clay dispersion in the presence of ionic species presents a challenge for preparing a transparent ionic nanocomposite (NC) hydrogel with the desired strength. A transparent ionic NC hydrogel was successfully prepared by in situ copolymerization of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and acrylamide (AAm) in the Laponite dispersion. AMPS played a dominant role in the dispersion of Laponite. Mechanical analyses demonstrated that this type of hydrogel has a combination of high tensile strength and excellent stretch ability. An increase in AMPS content made a big contribution to the tensibility, while an increase in clay content improved the elastic modulus. The ionic NC hydrogel exhibited a self-healing property, which occurred autonomously, without any outside intervention. The results showed that physical interaction among the NC hydrogels can be recovered. This work is a continuation of our previous efforts on the preparation and application of ionic NC hydrogels, for which there is a range of potential applications in soft and smart machines in the future.