Introduction of 9‐Bromo‐9‐Borafluorene Scaffold Into Deep Blue Emitting π‐Conjugated Polymers

ABSTRACT We report the first successful incorporation of 9‐bromo‐9‐borafluorene into a π‐conjugated co‐polymer consisting of 9,9‐silafluorene and 9,9‐dioctylfluorene units through a SiB exchange reaction. The parent 9,9‐silafluorene copolymer exhibits deep blue fluorescence, with CIE 1931 (0.15, 0.04), a high quantum yield ( Φ = 93.9%), and excellent thermal stability ( T 5d = 439°C). Density functional theory (DFT) calculations were employed to investigate the optical and electronic properties, revealing the structure of the molecular orbitals that contribute to the HOMO–LUMO bandgap of these conjugated co‐polymers. Additionally, we explored the Lewis acidity of the borafluorene unit and its potential for forming dynamic networks through reversible Lewis pair interactions, using 4,4′‐bipyridine as a model Lewis base. The integration of both silicon and boron into a π‐conjugated polymer backbone offers new opportunities for tuning the optical and electronic properties of materials for potential applications in OLED materials.