A chiral luminophore guided self-assembly of achiral block copolymer for ultra-amplification of circularly polarized luminescence

Circularly polarized luminescence (CPL) materials have been gaining significant attention due to their promising applications in 3D-displays, data-storage, optical switches, and biosensors. The CPL-active materials generally exhibit moderate signal of CPL with dissymmetry factors for photoluminescence (g_lum) in the range of 10^-5~10^-3, that may not serve the purpose for engineering applications. Herein, this work aims to demonstrate the feasibility to greatly amplify the chiroptical signals by self-assembly of achiral block copolymer (BCPs) polystyrene-b-poly(ethylene oxide) (PS-b-PEO) associated with chiral luminophores, R/S-1,1’-Bi-2-naphthol (R/S-BINOL), forming helix phase (H*) driven by chiral communication via host-guest interaction at various stages from self-assembly. Astonishingly, self-assembled H* exhibits ultra-amplification of the g_lum up to ~100 folds (g_lum ±0.3) as compared to the disordered phase resulting from the well-ordered helical arrangement of luminophores. Evidently, the CPL-activity is highly dependent on the self-assembled textures; note that for an achiral DG network phase with equal population of left-handed and right-handed domains, the symmetry restoration will nullify the effective chiroptical signals. This work provides a conceptual insight to utilize the mesochiral co-assembly of block copolymers with chiral luminophores, giving self-assembled phases in thin-film state for significant enhancement of dissymmetry factor.