Controlled Synthesis, Chiral Assembly, and Circularly Polarized Luminescence of Poly(Phenyl Isocyanide)-Block-Polyfluorene Copolymers

In this work, π-conjugated block copolymers consisting of poly(phenyl isocyanide) (PPI) and polyfluorene (PF) segments are facilely prepared by one-pot sequential polymerization of phenyl isocyanide (monomer 1) and 7-bromo-9,9-dioctylfluorene-2-boronic acid pinacol ester (monomer 2). The Pd(II)-terminated PPI is first prepared via polymerizing monomer 1 catalyzed with phenyl alkyne-Pd(II) complex and then utilized to initiate the controlled Suzuki cross-coupling polymerization of monomer 2, yielding various PPI-b-PF copolymers possessing controlled molar mass and narrow dispersity. Owing to the helical conformation of PPI segment and π-conjugated structure of PF segment, PPI-b-PF copolymers present distinctive optical property and fascinating chiral self-assembly behavior. During the self-assembly process, chirality transfer from helical PPI block to the supramolecular aggregates of helical nanofibers occurs to afford optically active helical nanofibers with high optical activity. Furthermore, the self-assembled helical nanofibers exhibit excellent circularly polarized luminescence performance.