Tunable mechanical and self-healing poly (acrylic acid-co-stearyl methacrylate) hydrogels induced by soaking methods

Due to the limitation of mechanical properties, the applications of traditional polymer hydrogels are seriously hindered in many fields. In this study, a series of hydrogels with controllable mechanical properties were successfully prepared by immersing the thermo-initiated poly (acrylic acid-co-stearyl methacrylate) hydrogels into LiCl, NaCl and KCl aqueous solution. The structural changes and properties of the gel before and after soaking were explored carefully by XRD, IR and Raman, etc. It was found that except for forming coordination interactions with the carboxyl group of acrylic acid, these salts can also promote the formation of hydrophobic associations consisted of long alkyl chains, which significantly improves the mechanical properties of the gel. The tensile strength and fracture energy of the KCl aqueous solution treated hydrogels could reach to 2.1 MPa and 19 MJ/m3, respectively, which are much higher than those of original hydrogels. Furthermore, the prepared hydrogels also have pressure sensitive conductivity, which could be used to detect body movements.