Simple and Versatile Protocol for Preparing Self-Healing Poly(vinyl alcohol) Hydrogels

As the role of polymers in undergraduate chemistry curricula continues to expand, opportunities will emerge for adopting experiments involving smart materials (i.e., materials that change properties in response to external stimuli). Slime demonstrations are routinely carried out with poly(vinyl alcohol) (i.e., PVA) hydrogels because the polymer is inexpensive and nontoxic, and the resulting material has interesting physical properties. This report describes an activity where PVA is processed into an autonomous self-healing smart material. Specifically, students prepare rigid PVA hydrogels using a simple freeze/thaw protocol. The resulting material is cut, and the severed edges are pressed together to initiate autonomous self-healing. Healing is observed by measuring sufficiently high (i.e., >40 kPa) uniaxial tensile strengths at the repaired surface. Preparing the hydrogel does not require chemical additives beyond commercially available PVA (i.e., Mw ∼ 145,000 g mol–1) and water. Additionally, the tensil...