Highly\nStretchable and Highly Resilient Polymer–Clay\nNanocomposite Hydrogels with Low Hysteresis

Abstract

Highly\nstretchable and highly resilient polymer–clay nanocomposite\nhydrogels were synthesized by in situ polymerization of acrylamide\nin the presence of pristine montmorillonite (MMT) or chitosan-treated\nMMT nanoplatelets at an elevated temperature. Both nanocomposite hydrogels\ncan be stretched to a strain of no less than 1290%. The treatment\nof clay with chitosan improves the tensile strength, elongation at\nbreak, and energy at break of the nanocomposite hydrogel by 237%,\n102%, and 389%, respectively, due to the strong chitosan–MMT\nelectrostatic interaction and the grafting of polyacrylamide onto\nchitosan chains. Both hydrogels display excellent resilience with\nlow hysteresis; with a maximum tensile strain of 50%, ultralow hysteresis\nis found, while, with a maximum strain of 500%, both hydrogels fully\nrecover their original state in just 1 min. The superb resilience\nof the nanocomposite hydrogels is attributed to the strong interactions\nwithin the hydrogels brought by chain branching, multiple hydrogen\nbonding, covalent bonding, and/or electrostatic force. The hydrogels\ncan be fabricated into different shapes and forms, including microfibers\nspun using pressurized gyration, which may find a variety of potential\napplications in particular in healthcare.