Polypyrrole nanomorphology-driven sodium alginate based multifunctional hydrogels: Synergistic integration of mechanical robustness, electromagnetic shielding, and strain sensing.

Abstract

Conductive hydrogels integrating mechanical reinforcement, electromagnetic shielding, and sensing functions have attracted considerable attention for multifunctional wearable electronics. Herein, a morphology-controlled polypyrrole (PPy) strategy was proposed to fabricate biochar (BC)-reinforced sodium alginate (SA) and polyacrylamide (PAM) semi-interpenetrating polymer network (semi-IPN) multifunctional conductive hydrogels. The results showed that the tubular PPy-based composite hydrogel, denoted as BSPH@PPy-Tube exhibited enhanced strength, stretchability, and toughness, with a tensile strength of 1.00 MPa, an elongation at break of 1486.43%, a modulus of 0.07 GPa, and a tensile toughness of 8.14 MJ·m-3. This improvement was attributed to the synergistic network among tubular PPy, BC, and the SA and PAM matrix, where tubular PPy served as conductive bridges and stress-transfer pathways, while hydrogen bonding, electrostatic interactions, and π-π stacking strengthen the interfacial interactions within the hydrogel. The interconnected tubular PPy and BC conductive network promoted electron transport, interfacial polarization, and multiple electromagnetic wave attenuation, achieving an EMI shielding effectiveness of 46.19 dB. The BSPH@PPy-Tube was further assembled as a flexible strain sensor, exhibiting a gauge factor of 5.07 in the 100-200% strain range and stable electrical responses to human motions. This work provides a feasible strategy for constructing multifunctional conductive hydrogels with mechanical robustness, electromagnetic protection, and wearable sensing capability.