Competing Dipolar and van der Waals Forces in Dynamic Self-Healing of Poly(Ionic Liquid) Copolymers

These studies elucidate the origin of molecular processes involved in the self-healing of imidazolium-based poly(ionic liquid) copolymers (PILCs) subjected to dynamic surface oscillating forces (SOF). In contrast to their counterpart homopolymers, which are either brittle or exhibit irreversible responses, PILCs composed of short (-CH₃; Me) and long (-CH)₂)₃CH₃; Bu) aliphatic side chains attached to the cation-anion pair composed of a 50/50 monomer molar ratio (poly(Me/Bu 50/50)) exhibit remarkable recovery. These dynamic responses arise from the competing polar and dipolar forces attributed to a balanced coexistence of ordered and disordered states involving the reversible rearrangements of H-bonding, ionic interactions, and London dispersion forces. These copolymer composition-driven processes exhibit dynamic recovery due to significant entropy increases, causing energy dissipation and reversible segmental rearrangements to achieve energetically favorable states. Spectroscopic FT-IR measurements combined with 2D correlation spectroscopic (2D-COS) analysis supported by molecular dynamics (MD) simulations reveal the significance of short- and long-forces involved in polar-dipolar interactions that enable dynamic recovery. The combination of directional and non-directional entropy-driven interchanges appears promising for identifying PILC architectures capable of mechanical adaptability, dynamic self-healing, and ionic conductivity.