Self-Healable Poly(ionic liquid) Copolymers Driven by Polar and Dipolar Forces

Commodity aliphatic and aromatic acrylic-based copolymers self-heal due to ubiquitous key-and-lock, ring-and-lock, and fluorophilic-σ-lock van der Waals (vdW) interactions. However, the role of these interactions in the presence of covalently copolymerized ionic liquid (IL) is not known. This study is driven by the hypothesis that covalently incorporated cation-anion pairs to form poly(ionic liquid) copolymers (PILCs) can perturb inter- or intra-chain vdW interactions reflected in mechanical and electrical responses. To test this hypothesis, we synthesized a series of PILCs comprising of pentafluorostyrene (PFS) and imidazolium-based IL monomers with variable-length aliphatic tails (methyl and butyl). Using a combination of 2D ¹H-¹H and ¹⁹F -¹⁹F NOESY NMR and FTIR measurements supplemented by molecular dynamic (MD) simulations, these studies demonstrate that preferentially alternating/random PILCs topologies facilitate self-healing. The introduction of cation-anion moieties modifies the fluorophilic-σ-lock interactions and, along with longer aliphatic tails ─(CH₂)₃CH₃ covalently attached to the imidazolium cation, enhances cation-anion mobility, thus faster recovery from mechanical damage occurs. These findings underline how precise control over dipolar and ionic interactions through copolymer composition enables self-healing in PILCs. These insights may open pathways for designing sustainable, mechanically resilient materials for applications in energy storage and energy harvesting.