Dual Crosslinking Double Network Smart Hydrogels of PVA–Borax and Crosslinked Poly( <scp>HEMA</scp> ‐Co‐ <scp>AA</scp> ) With Self‐Healing and Conducting Properties and Also Study of the Effect of First Network on the Double Network

ABSTRACT Dual crosslinking (both multiple physical and chemical crosslinks) approach was adopted to prepare double network (DN) smart hydrogels wherein PVA–borax complex having reversible physical crosslinking serves as first network, and chemical crosslinked copolymer of 2‐hydroxyethyl methacrylate and acrylic acid as second network. Such DN hydrogels not only exhibited pH‐responsive behavior but also good mechanical and self‐healing properties. The degree of swelling of DN hydrogels was observed to be lower than that of the single polymer network, which was further decreased with increasing PVA–borax content in the DN hydrogels. On the other hand, the mechanical properties of the hydrogels were improved with increasing concentration of PVA–borax in the DN hydrogels. A DN hydrogel having 10 wt% of PVA–borax with 25 wt% water content exhibited ~143% higher tensile strength (0.85 MPa) than that of the single network hydrogel (0.35 MPa). The toughness of the DN hydrogel was observed to be 1.244 N/mm 2 . Moreover, such tough hydrogels were made conductive by in situ polymerization of aniline within the porous structure of the DN hydrogels. The electrical conductivity of such a dry hydrogel (CDNH‐2) was observed to be 1.04 × 10 −3 S cm −1 , whereas it was 1.53 × 10 −3 S cm −1 in its swollen state. Such multifunctional mechanically tough, pH‐responsive, and conductive hydrogels may have several applications wherein self‐healing ability would become an added advantage.