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

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.