Objective  The polymer composite material made from lignin can improve the high additional utilization value of renewable lignin resources. If lignin is introduced into the hydrogel, not only the effective substitution of fossil raw materials in the hydrogel can be realized, but also the strength of the hydrogel can be improved, and the hydrogel can be given a variety of excellent properties.

  Method  Under alkaline conditions, a multifunctional sodium lignosulfonate@tannic acid-polyacrylic acid (TA@SL-PAA) hydrogel was produced using sodium lignosulfonate and tannic acid as raw materials and ammonium persulfate as initiator through in-situ reduction of Fe³⁺. It was proved by infrared spectrometer and scanning electron microscope that sodium lignosulfonate was successfully coated on the surface of tannic acid. Properties such as electrical conductivity, electrical conductivity, and self-healing properties were investigated.

  Result  Tannic acid was successfully loaded on sodium lignosulfonate to form a sodium lignosulfonate@tannic acid (TA@SL) complex. The sodium lignosulfonate@tannic acid hydrogel prepared from TA@SL had good mechanical properties. Under the best conditions, its elongation at break can reach 1 700%, and its compressive strength can reach 275 kPa. The hydrogel has high transparency and effective UV shielding effect, and the UV absorption capacity can reach 100%. In addition, due to the presence of sodium lignosulfonate and metal ions, the hydrogel also has excellent adhesion, self-healing ability, electrical conductivity and high sensitivity. It is worth mentioning that using the sensing properties of the hydrogel to prepare hydrogel electrodes can effectively capture stable electromyogram and electrocardiogram signal.

  Conclusion  Due to the good mechanical properties, electrical conductivity, and self-healing properties of sodium lignosulfonate@tannin hydrogels, it has great potential for applications in sensors, commercial electrodes, and wearable electrodes.