NIR‐II Excitable Semiconducting Polymers with AIE Characteristics for Fluorescence‐Photoacoustic Imaging‐Guided Synergistic Phototherapy

Abstract The development of semiconducting polymers (SPs) with simultaneous second near‐infrared (NIR‐II) absorption and multimodal phototheranostic functions is highly desired in the field of oncotherapy. Aggregation‐induced emission luminogens (AIEgens) have been acknowledged to possess unique potential in integrating multiple diagnostic and therapeutic modalities into one organic molecule. Nevertheless, SPs are hard to achieve AIE activity due to their extended π‐conjugated skeletons as well as the large and planar configuration of commonly‐used electrophilic acceptor moieties. Herein, an ingenious acceptor dimerization‐based acceptor distortion strategy is proposed in current work by taking advantage of the sterically encumbered acceptors with large and planar structure for the successful construction of AIE‐active SPs. Through further finely adjusting the molecular donor–acceptor interaction strength, one of the obtained AIE‐active SPs named SP3 bearing the highest intramolecular charge transfer effect presented desired NIR‐II absorption and aggregation‐induced NIR‐II fluorescence emission, good reactive oxygen species production ability, as well as superior photothermal conversion performance. Accordingly, SP3 is selected to fabricate into nanoparticles and successfully applied in the NIR‐II laser‐triggered fluorescence‐photoacoustic imaging‐guided photodynamic‐photothermal therapy of tumors. This study represents the first NIR‐II excitable AIE‐active SP, and offers a new perspective on designing advanced multimodal phototheranostic polymers for efficient treatment of malignant tumor.