Encoding Dipolar and Ionic Interactions in Comb-Like Poly(ionic Liquids)

Abstract

This study elucidates the origin of inter- and intrachain interactions in a new family of poly(ionic liquids) (PILs) containing alternating hydrophobic and hydrophilic groups terminated with variable-length aliphatic tails. The repeating units are sequentially synthesized and are composed of quadrupole (styrene), polar sulphonyl (−SO₂), dipolar aliphatic spacer, cation–anion pair, and variable-length aliphatic (methyl to n-butyl) tails. They participate in quadrupole (Q), dipolar (D), induced dipole (ID), ionic (C–A), and a combination of thereof interactions. When perturbed by polar H₂O molecules or electric fields (EFs), molecular events revealed by spectroscopic analysis supported by molecular dynamic (MD) simulations enabled encoding of the origin of intra- and interchain interactions and their impact on electrical responses. This study shows that conductivity increases for longer aliphatic tails, particularly when perturbed by H₂O, attributed to enhanced ID ⇔ H₂O interactions. At the same time, quadrupole interactions remain unchanged but enhance the mechanical integrity. Encoding the dynamics and strength of the Q ⇔ Q, D ⇔ D, ID ⇔ ID, and C–A interactions without generating protic environments may provide an opportunity for designing new generations of solid-state electrolytes exclusively relying on nonfaradic electrochemical processes that may lead to electrode decomposition or generation of undesirable side reactions.