Chiroptical Properties of Helical Aromatic Conjugated Polymers Synthesized by Electrochemical Polymerization in Chiral Nematic Liquid Crystals

Abstract

We synthesized several highly fluorescent fluorene derivatives, in which thiophene, biphenylthiophene, ethylenedioxythiophene (EDOT), or biphenyl EDOT moieties were attached at both ends of the fluorene moiety, and polymerized them via electrochemical polymerization in chiral nematic liquid crystals (N-LCs) providing asymmetric reaction environments. The resulting aromatic conjugated polymers showed induced chirality due to the formation of interchain helically stacked structures and hence exhibited circular dichroism (CD). The absorption dissymmetry factors (|gabs|) were in the range 10-4–10-2 and depended strictly on the moieties in the polymer chains. Some of the polymers exhibited circularly polarized luminescence (CPL) with luminescence dissymmetry factors (|glum|) of approximately 10-3. This is the first example of CPL from polymer films prepared by asymmetric electrochemical polymerization.