Polar Perturbations of Dipolar Interactions in Azole-Based Poly(ionic liquids)

Azole-based polymeric ionic liquids (PILs) containing imidazolium (Im) p(Im-TFSI) and triazolium (Tr) p(Tr-TFSI) ring cations naturalized by bis(trifluoromethane sulfonyl)imide (TFSI) anions were synthesized to elucidate the origin of dipolar-ionic interactions and their role in conductivity and mechanical properties. Spectroscopic analysis of p(Im-TFSI) and p(Tr-TFSI) PILs revealed that the presence of polar H₂O alters ionic and dipolar interactions, resulting in distinct ring-dependent hydration effects. In p(Tr-TFSI), more stable cation-anion-H₂O entities result from stronger electrostatic surface potentials (∼2 kcal/mol), where distinct separation of positive and negative electrostatic potentials in Tr-TFSI cation-anion pairs facilitates the formation of localized clusters inducing dipole-dipole interactions. In the presence of H₂O, ionic mobility is enhanced by solvating cation-anion pairs at the expense of weaker van der Waals interactions. The content of H₂O near Tr rings is higher, but there is restricted ionic mobility due to stronger polar forces that are formed at the expense of diminished induced dipole-dipole interactions. In contrast, in Im-based polymers, H₂O molecule associations with cation-anion pairs are weaker, and enhanced ionic mobility is reflected in increased conductivity values by a factor of 2. Both Im and Tr rings also facilitate distinct parallel resistor-capacitor (RC) responses with constant phase element (CPE) combinations; upon exposure to H₂O, the parallel RC circuits undergo configuration by an additional in-series connected R-CPE element.