Preparation of Optically Active Pyridine-Based Conducting Polymer Films Using a Liquid Crystal Electrolyte Containing a Cholesterol Derivative

Abstract

Optically active poly(1,4-di(2-thienyl)phenylene), poly(terthiophene), poly(bithiophene), and poly-(2,5-di(2-thienyl)pyridine) are successfully prepared by asymmetric electrochemical polymerization in a cholesteric electrolyte. The polymers thus synthesized are confirmed by polarizing optical microscopy to assume the doublespiral optical texture of the cholesteric liquid crystal electrolyte. In the reduced state, these polymers exhibit an intense Cotton effect in circular dichroism measurements. This optically active electrochromism is reversible by appropriate adjustment of applied voltage (redox state). Cyclic voltammetry measurements indicate that poly-(2,5-di(2-thienyl)pyridine) has an electrochemical n-dopable property.

Synthesis of a Terpene-Based New Chiral Inducer and Preparation of an Asymmetric Polymer

“…Cholesterol oleyl carbonate has been used as a chiral inducer (chiral dopant) [22,23]. However, twisting power of pure aliphatic chiral compounds tend to be weak due to flexibility of alkyl chain [24].…”

Preparation of iridescent-reflective poly(furan-co-phenylene)s by electrochemical polymerization in a cholesteric liquid crystal medium

“…The CLC electrolyte containing the monomer was injected between sandwiched indium tin oxide (ITO) coated electrodes (surface area: 1 cm × 5 cm) using a Teflon sheet (0.19 mm thick) as a spacer [21]. A constant direct current (DC) voltage of 4 V was then applied to the cell.…”

“…Electrochemical polymerization is a useful and convenient method that produces a polymer film on the electrode surface [16,17]. The polymers prepared by asymmetric electrochemical polymerization display intense circular dichroism (CD) in the reduced state, and weaker CD in the oxidized state [18][19][20][21].…”

Asymmetric electrochemical polymerization in cholesteric liquid crystalline media: Effect of isomeric structures of chiral inducers containing bornyl group

“…In this method, cholesteric liquid crystals (CLCs), a chiral liquid crystal with one-handed helical mesoscopic structure, are employed as reaction solvents. The molecular arrangement of CLCs can produce helical polymer backbones during polymerization [17]. Circular dichroism (CD) spectra of polymer films synthesized in a CLC solvent often show bisignate Cotton effect corresponding to a maximum optical absorption band due to chiral exciton coupling of polymer backbones via Davydov splitting.…”

“…In asymmetric electrochemical polymerization, the chiral inducer should be carefully chosen because macroscopic properties of the polymer film depend on environment produced by CLC electrolyte [18,19]. Cholesterol oleyl carbonate has been used as a chiral inducer in CLC electrolytes [16][17][18], but pure aliphatic chiral compounds tend to have low twisting ability because of conformational flexibility of the molecules [20]. For increasing the twisting ability, designed chiral inducers such as three-rings-type [19], chiral-octyl-type [21] and double-stereogenic-center-type [22] have been studied for effective asymmetric electrochemical polymerization.…”