Preparation and characterization of ionic conductive eutectogels based on polyacrylamide copolymers with long hydrophobic chain

With the blooming development of electronic technology, the use of electron conductive gel or ionic conductive gel in preparing flexible electronic devices is drawing more and more attention. Deep eutectic solvents are excellent substitutes for ionic liquids because of their good biocompatibility, low cost, and easy preparation, except for good conductivity. In this work, we synthesized a reactive quaternary ammonium monomer (3-acrylamidopropyl)octadecyldimethyl ammonium bromide with a hydrophobic chain of 18 carbons via the quaternization of 1-bromooctadecane and N-dimethylaminopropyl acrylamide at first, then we mixed quaternary ammonium with choline chloride, acrylic acid and glycerol to obtain a hydrophobic deep eutectic solvent, and initialized polymerization in UV light of 365 nm to obtain the ionic conductive eutectogel based on polyacrylamide copolymer with long hydrophobic chain. The obtained eutectogel exibits good stretchability (1200%), Young’s modulus (0.185 MPa), toughness (4.2 MJ/m³), conductivity (0.315 S/m). The eutectogel also shows desireable moisture resistance with the maximum water absorption of 11.7 wt% after one week at 25 °C and 60% humidity, while the water absorption of eutectogel without hydrophobic long chains is 24.0 wt%. The introduction of long-chain hydrophobic groups not only improves the mechanical strength of the gels, but also significantly improves moisture resistance of the eutectogel. This work provides a simpler and more effective method for the preparation of ionic conductive eutectogels, which can further provide a reference for the applications of ionic conductive eutectogels in the field of flexible electronic devices.