(255p) Anion Effects on the Structure and Ion Transfer Properties of Surface-Tethered Poly Ionic Liquids

Poly(ionic liquids) (PILs) refer to a special type of polyelectrolyte which carry an IL species in each of the polymer repeating units. PILs offer advantages over ILs in enhanced mechanical stability, improved processability, durability and spatial control over the IL moieties. The ability to grow surface-tethered polymer films with ionic liquid (IL) functionality as side chains can enable coatings with versatile and tailorable properties. Surface-tethered PILs were prepared via surface-initiated ring-opening metathesis polymerization (SI-ROMP) of norbornene-tethered ionic liquids to grow poly(ionic liquid) films on gold and silicon substrates. The PILs consist of the cations 1-norbornylmethylene-3-dimethylimidazolium (N1-dMIm⁺) or 1-norbornylpropyl-3-dimethylimidazolium (N3-dMIm⁺) with various anions that can be easily interchanged to tune the film properties. The choice of anion influences the structure and ion transfer properties of the films with the cation N1-dMIm⁺ only able to accommodate certain anions. Copolymer PIL films were prepared via the anion exchange of multiple anions into the PIL films. Polarization modulation-infrared reflectance-absorption spectroscopy (PM-IRRAS) was used to quantify the extent of anion exchange in the films. Profilometry measurements were utilized to quantify the thicknesses of the films. The dependence of ion transfer through the film on the ionic liquid anion was characterized by electrochemical impedance spectroscopy and cyclic voltammetry.