Strong and highly conducting PPyNT/PAA/PVA triple network hydrogel: scalable construction and strain sensing

Conducting polymer (CP) hydrogels that possess electronic and ionic conducting behaviors have attracted increasing attention as flexible electronic materials. Due to the insoluble and infusible nature of CPs (e.g., polyaniline (PANI), polypyrrole (PPy), etc.), the performance of their hydrogels is typically restricted, especially when the hydrogel was constructed through the in situ polymerization of aniline or pyrrole monomers. In this study, a method to prepare robust and highly conducting hydrogels at a large scale was developed with highly conducting PPy nanotubes (PPy NTs) and an interpenetrating network (IPN) of polyacrylic acid (PAA) and polyvinyl alcohol (PVA). The PVA/PAA IPN contains covalent cross-linking points, ionic coordination, and hydrogen bonding sites. This structure endows the hydrogel with excellent strength and toughness and provides effective stabilization for PPy NTs. The obtained PPyNT/PAA/PVA hydrogels exhibit tensile strengths higher than 4.0 MPa, and the conductivity reached 5.3 S m−1 with a PPy NT content of 0.63 wt%. As the PPy NTs effectively bonded with the hydrogel matrix network, the PPyNT/PAA/PVA hydrogels exhibit a linear relationship of conductivity change vs. strain in a wide strain range of 0–500%, with a steady gauge factor (GF) of ca. 1.38. Benefiting from preparation feasibility, the variation trends of hydrogel conductivity, deformation ability, and sensing properties were systematically studied, providing a reference for high-performance strain sensor materials.