Endowing the conventional HMPAM hydrogel with pH-responsive and self-healing properties

Stimuli-responsive materials are being developed at a rapid pace because of their many potential applications. Here, we report that the conventional responseless hydrophobically modified p(AM/C-12) hydrogel can be engineered to show fascinating pH-responsive and self-healing abilities simply in combination with a responser, sodium oleate (NaOA). The use of vesicle-to-micelle transition (VMT) of a surfactant by altering the pH in a narrow range endows the reversible sol-gel transition property to the conventional responseless hydrogel. As a result, we can modulate the rheological properties of the networks from highly elastic to viscous repeatedly, as well as vary the dynamic modulus over four orders of magnitude by simply adjusting the pH. Another particular interest is that such a vesicle-loaded hydrogel displays self-healing features through the autonomic reconstruction without the use of a healing agent. This type of pH-responsive self-healing hydrogel holds promise for the invention of new "smart" polymer materials.