The role of anions in light-driven conductivity in diarylethene-containing polymeric ionic liquids

Abstract

Polymeric ionic liquids (PILs) with light-driven conductivity represent a new class of smart materials with potential applications as soft electronics, however the influence of counterion characteristics on their conducting properties remains unexplored. We synthesized a series of PILs based on copolymers of ethylene oxide and allyl glycidyl ether with different anions and light-responsive imidazolium-containing diarylethene (DAE) cations. This study shows that anion character impacts the photostationary state (PSS), magnitude of conductivity, and light-responsive properties of PILs. Compared with BF₄⁻, anions featuring stronger cation–anion interaction (I⁻) and higher ratio of the ring-closed isomer at PSS (TFSI⁻) have a larger impact on the degree of change in ionic conductivity upon light irradiation. With this versatile synthetic platform, the electronic properties of the DAE cations can be non-invasively modulated by light with minimal structural change, providing the ability to study, in situ, cation–anion interaction without competing effects that arise from changes in polymer T_g or counterion size. These results are beneficial for understanding ion transport and structural design of smart light-responsive PILs.