Co-Assembly-Driven Chiral Induction of Well-Defined Polyfluorene-block-Poly(phenyl isocyanide) and Its Enhanced Circularly Polarized Luminescence Performance

Abstract

Chiral induction of polyfluorene (PF)-containing block copolymers plays a crucial role in the development of advanced functional materials; however, research in this area remains scarce. In this contribution, PFO-b-PPI diblock copolymers comprising blocks of poly(9,9-dioctylfluorene) (PFO) and poly(phenyl isocyanide) (PPI) were readily synthesized in one pot by combining chain-growth Suzuki cross-coupling polymerization of a modified 9,9-dioctylfluorene monomer with Pd(II)-catalyzed polymerization of a phenyl isocyanide monomer bearing a pentafluorophenyl ester substitute. The obtained PFO-b-PPI possessed a controlled molar mass (M_n) and narrow dispersity (M_w/M_n, Đ). Meanwhile, optically active supramolecular assemblies could be formed via coassembly of PFO-b-PPI with a chiral binaphthyl-based inducer in the film state after thermal annealing treatment, and the chirality of the supramolecular assemblies was influenced by the temperature of thermal annealing treatment, the weight ratio of the PFO-b-PPI copolymer to the chiral inducer, and the thickness of the film. Further investigations revealed that optically active supramolecular assemblies exhibited the morphology of single-handed helical nanofibers, and the helical sense of the nanofibers depended on the configuration of the binaphthyl-based inducer. Moreover, the supramolecular assemblies of helical nanofibers possessed excellent circularly polarized luminescence (CPL) performance with a g_lum as high as 0.11.