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

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Polymeric ionic liquids (PILs) are advanced materials with tunable properties.
• Understanding the interplay between ionic, dipolar, and hydration interactions is crucial for optimizing PIL performance.
• Azole-based cations, specifically imidazolium (Im) and triazolium (Tr), offer unique structural features.

Purpose of the Study:

• To synthesize and characterize azole-based PILs (p(Im-TFSI) and p(Tr-TFSI)).
• To elucidate the origin of dipolar-ionic interactions and their influence on conductivity and mechanical properties.
• To investigate the role of water (H₂O) in modulating these interactions and material behavior.

Main Methods:

• Synthesis of imidazolium and triazolium-based PILs with bis(trifluoromethane sulfonyl)imide anions.
• Spectroscopic analysis to study interactions and hydration effects.
• Electrochemical impedance spectroscopy to analyze conductivity and dielectric responses.

Main Results:

• Spectroscopic analysis revealed distinct, ring-dependent hydration effects in p(Im-TFSI) and p(Tr-TFSI) PILs.
• p(Tr-TFSI) showed stronger cation-anion-H₂O interactions and localized clustering, leading to restricted ionic mobility despite higher H₂O content.
• p(Im-TFSI) exhibited weaker H₂O associations, resulting in enhanced ionic mobility and a twofold increase in conductivity.
• Both PIL types displayed unique parallel resistor-capacitor (RC) responses, which reconfigured upon H₂O exposure.

Conclusions:

• Dipolar-ionic interactions and hydration significantly influence the conductivity of azole-based PILs.
• The specific azole ring structure (Im vs. Tr) dictates the hydration mechanism and its impact on ionic mobility and conductivity.
• Water acts as a plasticizer, enhancing ionic mobility by solvating cation-anion pairs, but its effect is modulated by the strength of polar interactions.