A robust-switchable poly(vinyl alcohol) gel with adjustable multiple hydrogen bonding interactions

It is highly desirable to develop gels possessing exceptional and adjustable mechanical properties, self-healing performance, recycling behavior, etc., simultaneously. In this study, a poly(vinyl alcohol)/tannic acid (PVA/TA) gel with extraordinary mechanical properties (∼4.9 MPa, ∼950%) was prepared by forming crystalline regions and multiple hydrogen bonds. More interestingly, the strength/elongation and shape of the gel could be continuously and regularly regulated. Take the 15% PVA/TA gel as an example, its mechanical strength can be freely and consecutively converted between about 0.36 MPa and around 0.80 MPa. Besides, the PVA/TA gel can be served as a sensor with rapid responsiveness (Response time ∼ 165 ms and recovery time ∼ 151 ms) to monitor the changes of strain in real time when ferric chloride is added. Specifically, the gel can still effectively monitor the human motions after self-healing and recycling. This study provides an important reference value for the preparation of gels with high and adjustable mechanical properties, self-healing performance, recycling behavior, etc.