Light-Switchable and Self-Healable Polymer Electrolytes Based on Dynamic Diarylethene and Metal-Ion Coordination

Abstract

Self-healing polymer electrolytes are reported with light-switchable conductivity based on dynamic N-donor ligand-containing diarylethene (DAE) and multivalent Ni2+ metal-ion coordination. Specifically, a polystyrene polymer grafted with poly­(ethylene glycol-r-DAE)­acrylate copolymer side chains was effectively cross-linked with nickel­(II) bis­(trifluoromethanesulfonimide) (Ni­(TFSI)2) salts to form a dynamic network capable of self-healing with fast exchange kinetics under mild conditions. Furthermore, as a photoswitching compound, the DAE undergoes a reversible structural and electronic rearrangement that changes the binding strength of the DAE–Ni2+ complex under irradiation. This can be observed in the DAE-containing polymer electrolyte where irradiation with UV light triggers an increase in the resistance of solid films, which can be recovered with subsequent visible light irradiation. The increase in resistance under UV light irradiation indicates a decrease in ion mobility after photoswitching, which is consistent with the stronger binding strength of ring-closed DAE isomers with Ni2+. 1H–15N heteronuclear multiple-bond correlation nuclear magnetic resonance (HMBC NMR) spectroscopy, continuous wave electron paramagnetic resonance (cw EPR) spectroscopy, and density functional theory (DFT) calculations confirm the increase in binding strength between ring-closed DAE with metals. Rheological and in situ ion conductivity measurements show that these polymer electrolytes efficiently heal to recover their mechanical properties and ion conductivity after damage, illustrating potential applications in smart electronics.

Future‐Oriented Advanced Diarylethene Photoswitches: From Molecular Design to Spontaneous Assembly Systems

“…For example, on the basis of their previous exploration of polymer ionic liquids containing DAE, [140] Segalman et al reported a self-healing polymer electrolyte based on nickel complexes. [141] The prepared material exhibited good mechanical properties, so they expected it to be easy to apply to equipment. The introduction of the DAE unit allowed the conductivity of the assembly system to be altered by light.…”

“…Integrating molecular components into digital circuits is an effective strategy for endowing devices with functionalization, [ 141 ] and stimulus‐responsive molecules with the capacity to transition between two or more states are particularly interesting. If such molecules were combined into a conventional FET, the resulting devices could have new stimulus‐response capacities for use in advanced electronics such as memory devices, sensors, and smart gates.…”

“…By integrating light‐responsive moieties into the structure of polymer electrolytes, the rational and noninvasive modulation of weak interactions, such as cation–anion, polymer–ion, and Lewis acid–base interactions, is an attractive approach to tune ion mobility and conductivity in situ. Recently, Segalman and co‐workers [ 141 ] developed a photoswitchable polymer ionic liquid based on imidazolium‐containing DAE cations. When they tuned the positive charge distribution and cation‐action interactions using light irradiation, they observed that ionic conductivity could be reversibly modulated.…”

“…e) Molecular structure and schematic of a metal-salt-added polymer network. Reproduced with permission [141]. Copyright 2021, American Chemical Society.…”

Basic physicochemical processes governing self‐healable polymers†

“…Taking advantage of the coordination between Fe 3+ and catechol ligands, pH‐induced crosslinked self‐healing polymers with near‐covalent elastic moduli were developed 63 . Metal ion coordination between multivalent Ni 2+ and dynamic N‐donor ligand containing diarylethene facilitate the development of light‐switchable and self‐healable polymer electrolytes 64 . Hydrophobic cavities of cyclodextrins can also be used to bind and trap other molecules inside them.…”