Poly (aryl sulfone)s containing 5,11-dihydroindolo[3,2-b] carbazole moieties in the main chain: non-conjugated blue-light-emitting materials

Abstract

Three types of non-conjugated homopolymer with blue light emission containing 5,11-dihydroindolo[3,2-b]carbazole derivatives in the main chain were prepared via an N–C coupling reaction. Compared with the conjugated small molecule 5,11-dihydroindolo[3,2-b]carbazole derivatives, the emission spectra showed a blue shift after the introduction of nonconjugated diphenyl sulfone as the electron-deficient unit. Meanwhile, the rigid and twisted configuration of the polymers possesses the characteristic of large steric hindrance, which can effectively avoid the aggregation-caused quenching (ACQ) phenomenon in the solid state. From a test of the redox potential and DFT calculations of the small molecular monomers and polymers, the electron distribution and the molecular orbital (HOMO–LUMO) change of 5,11-dihydroindolo[3,2-b]carbazole derivatives with the introduction of electron-withdrawing and electron-donating units was revealed. The non-conjugated polymers exhibited excellent thermal stability and solubility, endowing them with good application prospects. The resultant polymers with different side groups showed blue light emission spectra from 427 nm to 461 nm. This facile and versatile strategy to synthesize non-conjugated polymers with blue light-emission leads to a new avenue for highly efficient and stable blue OLEDs.