Red and Robust: Highly Stable Electrofluorochromic Switching in Cyano‐Substituted Aggregation‐Induced Emission‐Active Conjugated Polymers

Abstract Research interest in electrofluorochromic (EFC) polymers is rapidly growing, yet significant gaps remain, notably the scarcity of red‐emitting EFC polymers and the need to improve long‐term switching stability. Both challenges may be addressed by incorporating electron donor and acceptor monomers into conjugated polymers. Herein, three pairs of isomeric conjugated polymers featuring different nitrile group distributions are synthesized. Among them, only the pair incorporating α‐cyanostilbene acceptors exhibited red fluorescence with pronounced aggregation‐induced emission (AIE) characteristics, whereas polymers bearing α,β‐dicyanostilbene and 3,3′‐(1,4‐phenylene)bis(2‐phenylacrylonitrile) units are non‐emissive. Computational studies are conducted to elucidate the structure–property relationships. Detailed EFC property studies of the two red‐emissive AIE polymers, p(g‐1CN) and p(v‐1CN), revealed robust EFC performance, with reversible red fluorescence quenching (λ _em = 624 and 622 nm) under ±1.2 and ±1.4 V, respectively. The polymers achieved comparable contrast ratios (I _OFF/ON ) of 9.7 and 11.6 and exhibited faster switching response times than their uncyanated stilbene‐based analogues, which can be further improved by incorporating ethyl viologen into the devices. Both polymers demonstrated outstanding operational stability, maintaining performance over 2500 cycles, with p(v‐1CN) remaining functional after 10 000 cycles. These results represent the most red‐shifted emissions and the highest switching stabilities reported for AIE‐active EFC polymers to date.