Metal-Containing Poly(ionic liquid) Exhibiting Photogeneration of Coordination Network: Reversible Control of Viscoelasticity and Ionic Conductivity

Abstract

The control of physical properties of soft matters via external stimuli is useful for various applications. Poly(ionic liquid)s are versatile liquid polymers exhibiting ionic conductivity, though the development of photoresponsive poly(ionic liquid)s is still limited.Here we report the synthesis and properties of a photoreactive poly(ionic liquid) 1a consisting of a Ru sandwich complex [Ru(C5H5){C6H3(OC6H12CN)3}] + and a polymeric anion -[-CH2-CH(SO2N − SO2CF3)-]n-. Upon UV photoirradiation, the liquid transformed to a rubbery elastomer 2a through the photochemical reaction of the cations. The resultant elastomer is a unique hybrid coordination polymer comprising of a cationic coordination network and anionic covalent chains. The elastomer returned to 1a upon heating. The application of light and heat resulted in a coordination structure transformation that caused reversible changes in viscoelasticity and ionic conductivity. The liquid 1a was synthesized by polymerization of ionic liquid 1b containing an H2C=CHSO2NSO2CF3 − anion. UV photoirradiation transformed 1b into a viscous elastomer 2b consisting of a coordination network, though the elastomer changed into 1a upon heating via polymerization of the anion.

Metal–Organic Network-Forming Glasses

“…Another Ruc o n t a i n i n g p o l y ( i o n i c l i q u i d ) , [ R u ( C 5 H 5 ) -[C 6 H 3 (OC 6 H 12 CN) 3 ]] + , and a polymeric anion, [CH 2 − CH(SO 2 N−SO 2 CF 3 )] n , undergo a UV-induced phase transition. 175 UV irradiation initiates the photochemical reaction of the cation, resulting in a cationic coordination network and anionic covalent chains (T g = −8 °C). In addition to the synthesis of ionic liquids, the formation of 2D and 3D crystalline anionic CPs containing organometallics and ionic liquids has been demonstrated.…”

On-demand gelation of ionic liquids using photoresponsive organometallic gelators

“…47,48 We previously developed several photoreactive ILs using this mechanism. [49][50][51][52][53] As shown in Fig. 1c, after the addition of a small amount of 1-X, various ILs transformed to ionogels upon UV irradiation.…”

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

“…The ability to remotely modulate ion and/or charge transport using light not only is essential for neurological activity in nature but also enables the fabrication of multifunctional smart materials including photoswitchable organic light-emitting transistors, supramolecular hydrogels, metal organic frameworks, and semiconductors . By introducing light-responsive functional groups into these materials, the optical and/or electrical properties can be noninvasively tuned with excellent spatial and temporal resolution, making them pivotal components for emerging optoelectronics applications such as smart displays, photodetectors, and logic circuits. ,− Among these materials, polymer electrolytes are an attractive platform due to their high ionic conductivity, tunable polymeric scaffold, and robust mechanical properties. , Importantly, ion mobility and conductivity in these materials are highly dependent on different types of weak interactions, such as cation–anion, polymer–ion, and Lewis acid–base interactions. , The rational and noninvasive modulation of these weak interactions by integrating light-responsive moieties into the structure of polymer electrolytes provides an elegant way to tune the ion mobility and conductivity in situ. , Huang and co-workers reported supramolecular ion-conducting hydrogels using azobenzene to mediate reversible changes in conductivity by competitive guest–host interactions. ,, We recently developed a photoswitchable polymeric ionic liquid based on imidazolium-containing diarylethene (DAE) cations and observed that ionic conductivity can be reversibly modulated by tuning the positive charge distribution and cation–anion interaction upon light irradiation . However, current light-responsive ion-conducting polymer electrolytes have relatively poor solid-like mechanical properties, because they are either viscous liquids with a low glass-transition temperature ( T g ≪ 20 °C) or solvent-containing hydrogels. , Consequently, the materials are difficult to integrate into devices. − The development of light-responsive, ion-conducting polymers that are mechanically robust, capable of self-healing, and inherently tunable remains a major challenge.…”

“…13,14 The rational and noninvasive modulation of these weak interactions by integrating light-responsive moieties into the structure of polymer electrolytes provides an elegant way to tune the ion mobility and conductivity in situ. 15,16 Huang and co-workers reported supramolecular ion-conducting hydrogels using azobenzene to mediate reversible changes in conductivity by competitive guest−host interactions. 3,17,18 We recently developed a photoswitchable polymeric ionic liquid based on imidazolium-containing diarylethene (DAE) cations and observed that ionic conductivity can be reversibly modulated by tuning the positive charge distribution and cation−anion interaction upon light irradiation.…”