Ultrasound assisted lignin-decorated MWCNT doped flexible PVA–Chitosan composite hydrogel

This study reports a facile ultrasound-assisted synthesis and characterization of physically-crosslinked polyvinyl alcohol (PVA)-chitosan conductive hydrogels with lignin-decorated multi-walled carbon nanotube (MWCNT) as nanofiller. Homogeneous dispersion of MWCNT in the hydrogel matrix was achieved through the addition of lignin nanoparticles (optimum LP:MWCNT ratio of 2:1) in presence of acetone, followed by sonication of the mixture. FETEM images reveal lignin particles adhere onto the surface of the MWCNT, which assists de-agglomeration and dispersion of MWCNT in the aqueous medium. The hydrogels produced were mechanically stable and flexible in nature. The elastic moduli (G′) of hydrogels with 0.5 and 1 wt% MWCNT were 11170 and 11757 Pa, respectively, whereas the tensile strengths were 2.22 and 2.56 MPa. Further, addition of lignin (1 and 2 wt%) and MWCNT (0.5 and 1 wt%) imparted thermal stability to PVACS hydrogels. FESEM images confirmed the porous internal structure of the hydrogel with mesh size ∼7 nm for 1 wt% MWCNT content. The hydrogel with 1 wt% MWCNT possessed the highest conductivity (8.22 mS cm−1) among all the other hydrogels. These hydrogels have potential applications as electrodes or electrolytes for energy storage devices, ECG electrodes, and flexible sensors.