Preparation of amphoteric nanocomposite hydrogels based on exfoliation of montmorillonite via in-situ intercalative polymerization of hydrophilic cationic and anionic monomers

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.