Dynamics of Dipolar and Ionic Interactions in Self-Healable Poly(ionic liquid) Copolymers

Loosely classified as supramolecular (H-bonding, coordination, ionic bonding), dipole–dipole and dipole–induced dipole interactions are ubiquitous inter- and intramolecular forces responsible for many polymer properties. Many combinations of these interactions are often produced by nature and manifest hydrophilic and hydrophobic properties involving ionic and aliphatic/aromatic entities. Built on the hypothesis that dynamics of dipolar and ionic interactions in copolymers may exasperate each other, we copolymerized a series of ionic liquids composed of variable-length aliphatic tails attached to cation–anion pairs with commodity monomers and examined their response to external forces. These studies show that the length, flexibility, and mobility of aliphatic tail ends facilitate the enhanced dipole–dipole inter- and intrachain interactions and empower the formation of anion-pair channels. Combined with spectroscopic analysis supported by molecular dynamic (MD) simulations, these synthetic efforts identified dynamics of ion–ion, dipole–dipole, and ion–dipole inter- and intrachain interactions responsible for tuning electrical properties and autonomous response to mechanical perturbation. These studies also show how minute chemical changes in aliphatic tails covalently bonded to ionic groups induce inter- and intrachain van der Waals (vdW) and polar forces.