Chiroptical Resolution and Thermal Switching of Chirality in Conjugated Polymer Luminescence via Selective Reflection using a Double-Layered Cell of Chiral Nematic Liquid Crystal

An optically resolvable and thermally chiral-switchable device for circularly polarized luminescence (CPL) is first constructed using a light-emitting conjugated polymer film and a double-layered chiral nematic liquid crystal (N*-LC) cell. The double-layered N*-LC cell with opposite handedness at each layer is fabricated by adding each of two types of N*-LCs into each of the cells, and the N*-LCs consist of nematic LCs and chiral dopants with opposite chirality and different mole concentrations. The selective reflection band due to the N*-LC is thermally shifted so that the band wavelength is close to the luminescence band of the racemic conjugated polymer, such as disubstituted polyacetylene (diPA), yielding CPL with opposite handedness and high dissymmetry factor values (vertical bar glum vertical bar) of 1.1-1.6 at low and high temperatures. The double-layered N*-LC cell bearing the temperature-controlled selective reflection is useful for generating CPLs from racemic fluorescent materials and for allowing thermal chirality-switching in CPLs, which present new possibilities for optoelectronic and photochemical applications.