Extremely Soft, Conductive, and Transparent Ionic Gels by 3D Optical Printing

A series of 3D printable multifunctional ionic gels (IGs) are developed incorporating ionic liquid (IL) in the thiol–ene network of thiol-based end-crosslinker and acrylate monomers. The resulted gels, termed as thiol-ionic gels (T-IGs), are highly transparent and very soft with IL content of 70–85 wt%. The mechanical and conductive properties of the T-IGs are found to be largely dependent on the IL content, end-crosslinker functionalities, and chain-length of monomers. Progression of ionic conductivity is observed with an increase in IL content and conductivity as high as 5.40 mS cm⁻¹ is attained for longer acrylate group containing T-IGs at room temperature, while further increase is observed at elevated temperature. T-IGs in all systems are found to exhibit superior thermal stability. Three-dimensional fabrication of these functional T-IGs is achieved by optical 3D printing process with microscale resolution in facile steps.