Synchronously Manipulating Absorption and Extinction Coefficient of Semiconducting Polymers via Precise Dual‐Acceptor Engineering for NIR‐II Excited Photothermal Theranostics

Integrating the ultralong excitation wavelength, high extinction coefficient, and prominent photothermal conversion ability into a single photothermal agent is an appealing yet significantly challenging task. Herein, a precise dual-acceptor engineering strategy is exploited for this attempt based on donor-acceptor (D-A) type semiconductor polymers by subtly regulating the molar proportions of the two employed electron acceptor moieties featuring different electronic affinity and π-conjugation degrees, and making full use of the active intramolecular motion-induced photothermal effect. The optimal polymer SP4 synchronously shows desirable second near-infrared (NIR-II) absorption, an extremely high extinction coefficient, and satisfactory photothermal conversion behavior. Consequently, the unprecedented performance of SP4 NPs on 1064 nm laser-excited photoacoustic imaging (PAI)-guided photothermal therapy (PTT) is demonstrated by the precise tumor diagnosis and complete tumor elimination.