Synthesis and Optoelectronic Properties of Branched Polystyrene-graft-Polyfluorene Copolymers

Poly(9,9-di-n-octylfluorene) (PFO) applications are limited by green emission defects and imbalanced charge transport. To overcome this, novel branched polystyrene-graft-polyfluorene (PSt-g-PFO) copolymers with varying grafting densities were synthesized. The highly branched architecture induces intense steric hindrance, acting as a physical shield to isolate PFO emissive cores. This successfully suppresses detrimental interchain π–π stacking, mitigating the ~530 nm green emission. Furthermore, the moderately grafted PSt-g-PFO2 promotes locally ordered crystalline packing, achieving a maximum electron mobility of 6.16 × 10−6 cm2/(V·s), an order of magnitude higher than linear PFO. This structural design effectively decouples deleterious aggregation from charge transport.