Robust imogolite hydrogels with tunable physical properties

Mechanically tough hydrogels with tunable physical properties (i.e., mechanical strength and stimuli responsiveness) were obtained by in situ copolymerization of various vinyl monomers such as acrylic acid (AA), 2-hydroxyethyl acrylate (HEA), acrylamide (AAm), and N-isopropylacrylamide (NIPA) in an aqueous media containing imogolite (IG), an aluminosilicate nanotube clay. In situ copolymerization of AA and NIPA in the presence of IG gave robust hydrogels that showed thermo-responsive volume change owing to coil/globule transitions of the NIPA fragments. Furthermore, the mode of interaction between IG and the organic polymer was critical for determining the mechanical properties of the resultant hydrogel. Thus, IG gels with tunable physical properties were produced by designing the molecular structure of polymers, i.e., by modulating the strength of the interaction between IG nanotubes and organic polymer units.