Polyfluorene Containing Dibenzothiophene‐ S,S ‐Dioxide and Benzothiadiazole Units for Fluorescent Response to Metal Ions

ABSTRACT

The green light‐emitting polymer (PF‐SO10‐BT1) was prepared by the Suzuki polycondensation method, during which dibenzothiophene‐ S,S ‐dioxide (SO) and 2,1,3‐benzothiadiazole (BT) units were incorporated into the polyfluorene (PF) backbone. Both the SO and BT units possessed strong electron‐deficient ability in PF‐SO10‐BT1, which can form a donor/acceptor structure with the fluorene unit, exhibiting intramolecular charge transfer (ICT) characteristics. The number‐average molecular weight ( M _n ) of PF‐SO10‐BT1 was 36.5 kDa with a polydispersity index (PDI) of 2.08. This molecular weight was beneficial for dissolution in polar solvents while also being able to achieve green light emission through the ICT effect. The photoluminescence quantum yield ( Φ _PL ) of PF‐SO10‐BT1 in N,N ‐dimethylacetamide solution was as high as 77.6%, which can provide sufficient fluorescence signal intensity under low concentration conditions. PF‐SO10‐BT1 exhibited cross‐sensitivity under gradual addition of metal ion solutions with multiple mixing cycles, whereas distinct response behavior was observed after the direct addition of metal ion solutions with a single mixing cycle. The limit of detection (LOD) of PF‐SO10‐BT1 for Fe ³⁺ was 20.7 µM. These results provide insights into the structure–property relationships of conjugated polymers incorporating the SO and BT units and valuable guidance for the further structural design of analogous conjugated polymers.