Multicolor circularly polarized luminescence: pendant primary amine/diphenylalanine chiral copolymers with clustering-triggered emission

Abstract

Clustering-triggered emission (CTE) materials without π-conjugate chromophores have attracted increasing attention, because of their nonconventional emission properties and wide applications. However, circularly polarized luminescence (CPL) in CTE materials has been less explored. In this study, we designed CTE-based CPL block and random copolymers comprising vinyl amine and N-acryloyl-L,L-diphenylalanine. These CTE-based chiral copolymers exhibited concentration- and excited-wavelength-dependent emissions in water. By introducing a charged fluorescent dye (thioflavin T (ThT) or rose bengal) into the copolymer aqueous solution, a red-shifted emission color was detected as the amount of fluorescent dye owing to the fluorescence resonance energy transfer (FRET) between the dye and block copolymers via electrostatic interactions. The chirality of block copolymer was transferred into achiral ThT, as confirmed by ThT-induced circular dichroism. The thin film of CTE-based chiral block copolymer and block copolymer/ThT exhibited CPL, and the chirality of ThT was amplified with the highest emission dissymmetry factor (g_lum) of −0.0099. This study provides a new perspective on CTE-based CPL polymeric materials, showing CTE-CPL properties in solid states and multicolor CPL by FRET via electrostatic interactions.