Polypyrrole/PU hybrid hydrogels: electrically conductive and fast self-healing for potential applications in body-monitor sensors

Abstract

Conductivity, self-healing and moderate mechanical properties are necessary for multifunctional hydrogels, which have great potential in health-monitor sensor applications. However, the combination of electrical conductivity, self-healing and good mechanical properties to hydrogels is still a huge challenge. To solve this issue, we prepared a new kind of polyurethane (PU) hydrogel using 4-aminophenyl disulfide (APDS) as the chain extender, which endowed PU hydrogels with fast self-healing property, owing to dynamic disulfide bonds embedded in hard segments. In addition, the rigid benzene ring contained in the chain extender provided PU hydrogels with good mechanical properties. Moreover, the conductive component polypyrrole (PPy) was incorporated by in situ polymerization to impart the conductivity performance. A nonporous surface of PU hydrogels processed was found by freeze-drying. This was due to the short-chain PEG soft segment and the unique microphase separation structure of polyurethane. The obtained optimal PU/APDS/PPy (PUASPy) hybrid hydrogels combined multifunctionality with certain conductivity (0.055 S m⁻¹), rapid self-healing property, moderate mechanical strength (tensile stress of 1.1 MPa), flexible stretchability (sensing range >500%), and rapid mechanical recovery (10 min). The excellent characteristics of hydrogels are further illustrated by being used as a large-scale human motion monitoring sensor. This work provides an effective approach to prepare a multifunctional PU hydrogel for broadening their application including wearable devices and responsive electrical devices.