Adhesive and conductive hydrogels based on poly(acrylic acid) composites for application as flexible biosensors

A PAA (polyacrylic acid)-based nanocomposite hydrogel (CASM) reinforced with sodium carboxymethyl cellulose (CMC-Na), organo-montmorillonite (OMMT), and sodium lignosulfonate (SLS) was prepared using free radical polymerization. In this work, CMC-Na was utilized to enhance the viscosity of the system, while the electrostatic interaction between CMC-Na and OMMT facilitated the uniform dispersion of OMMT within the matrix. Additionally, SLS aided in the dispersion of the components, reducing the interaction forces between particles in the hydrogel, thereby improving its flexibility and extensibility. The results demonstrated that the synergistic effects of CMC-Na, OMMT, and SLS led to a hydrogel with a tensile strength of up to 74.5 KPa, a tensile strain exceeding 3600%, and certain shape memory properties. Furthermore, the incorporation of SLS, which provides phenolic hydroxyl and sulfonic groups, significantly enhanced the adhesive properties of the hydrogel, achieving a peel strength of up to 1200 N/m on aluminum. The sulfonic groups also facilitated ion transport, resulting in excellent electrical conductivity (9.82 mS/cm) and strain sensitivity (GF=4.36). This approach of improving hydrogel properties through the incorporation of inorganic particles and cross-linked structures offers a novel strategy for the multifunctional modification of hydrogels.