writer：Guorong Gao, Gaolai Du, Yuanna Sun, and Jun Fu
keywords：nanocomposite hydrogels, tough, stretchable, self-heal, montmorillonite
source：期刊
specific source：ACS Applied Materials and Interfaces, DOI: 10/1021/acsami.5b00704
Issue time：2015年

Nanocomposite hydrogels with unprecedented stretchability, toughness, and self-healing have been developed by in situ polymerization of acrylamide with the presence of exfoliated montmorillonite (MMT) layers as non-covalent crosslinkers. The exfoliated MMT clay nanoplatelets with high aspect ratio, as confirmed by TEM and XRD results, are well dispersed in the polyacrylamide matrix. Strong polymer/MMT interaction was confirmed by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The effective crosslink densities of these hydrogels are estimated in the range of 2.2 – 5.7 mol m^–3. Uniaxial tensile tests showed a very high fracture elongation up to 11 800 % and a fracture toughness up to 10.1 MJ m^–3. Cyclic loading-unloading tests showed remarkable hysteresis, which indicates energy dissipation upon deformation. Residual strain after cyclic loadings could be recovered under mild conditions, with the recovery extent depending on clay content. A mechanism based on reversible desorption/adsorption of polymer chains on clay platelets surface is discussed. Finally, these nanocomposite hydrogels are demonstrated to fully heal by dry-reswell treatments.