Chiral BEDOT-based copolymers prepared by chemical and electrochemical polymerization

Abstract Optically active conjugated copolymers, poly[1,4-bis[2-(3,4-ethylenedioxy)thienyl]-2,5-benzoic acid-1-methylheptyl ester] [poly (BEDOT-B(OCT*)], were synthesized by chemical and electrochemical oxidative polymerizations. Poly[BEDOT-B(OCT*)] of both ( R ) and ( S ) configuration were synthesized by introducing chiral octyloxycarbonyl group in the side chain. The dibromo compounds, ( R )-1 and ( S )-1, were prepared by Mitsunobu reaction by an esterification of ( R ) or ( S )-octanol and 2,5-dibromobenzoic acid with an aid of diethyl azodicarboxylate (DEAD) and triphenylphosphine (TPP) in tetrahydrofuran. The monomers were then prepared with Stille coupling technique using Pd(PPh 3 ) 4 Cl 2 as a catalyst to produce ( R )-1 and ( S )-1. The monomer was electropolymerized onto platinum button and ITO glass electrodes by repeated scanning from −1.0 V to +1.0 V versus Ag/Ag + at 20 mV/s. The polymer was electrochromic and reversibly switching from purple green upon oxidation. The chemical polymerization was also carried out in dimethylformamide with a Ni(cod) 2 catalyst. Optical absorption and circular dichroism (CD) measurements were examined. The polymers showed Cotton effects in CD spectra. This method therefore represents a new technique for the preparation of chiral polymer with helicity, which can disclose a possibility toward “chiralelectrochemistry”.