Mechanical and Self-Healing Properties of Poly Acrylic Acid/Laponite/Fe3+ Nanocomposite Hydrogel

A type of self-healing composite hydrogel with a dual physical cross-linking property was prepared by one-step polymerization. Scanning electronic microscopy (SEM) measurements showed that the microstructures of these composite hydrogels are three-dimensional networks of densely packed pores. The hydrogel networks consist of two types of noncovalent interactions, hydrogen bonds and ionic interactions, which were revealed by Fourier transform infrared (FT-IR) spectroscopy and DSC analysis. Thus, by varying Fe3+ and Laponite concentration, the mechanical properties of composite hydrogels can be determined. Tensile stress-strain and loading-unloading tests were employed to characterize the mechanical properties of the composite hydrogels. It was found that the optimal composition of hydrogels, PAA/Laponite-5.0/Fe3+-0.5, exhibited excellent mechanical properties. Because the ionic coordinates between ferric ions and -COO- of PAA could serve as special dynamic junction points, the mobility of free ferric ions imparts self-healing properties to the hydrogels. Additionally, the self-healing efficiency of the hydrogels is largely dependent on the concentration of the ferric ions.