Facile electrosynthesis of novel free-standing electroactive poly((S)-(−)-1,1′-bi-2-naphthol dimethyl ether) films with enhanced main chain axial chirality

Direct anodic oxidation of (S)-(−)-1,1′-bi-2-naphthol dimethyl ether (BNME) in CH₂Cl₂/CHCl₃ containing boron trifluoride diethyl etherate (BFEE) as the supporting electrolyte led to facile electrodeposition of high-quality free-standing poly((S)-(−)-1,1′-bi-2-naphthol dimethyl ether) (PBNME) film on stainless steel (SS)/indium tin oxide (ITO) electrodes. As-formed PBNME films showed good electroactivity and redox stability in CH₂Cl₂-BFEE, BFEE, and even in concentrated sulfuric acid. Both doped and dedoped PBNME films were partly soluble in strong polar solvents, such as dimethyl sulfoxide (DMSO). Quantum chemistry calculations of BNME and FT-IR spectrum of dedoped PBNME films demonstrated that the polymerization probably occurred at 4- and 4′-positions. Optical rotation determination showed that the conformation of the monomer was maintained during the electrochemical polymerization process and the polymer exhibited greatly enhanced optical rotation value with main chain axial chirality compared with that of the monomer. Fluorescent spectral studies indicated that soluble PBNME was a good blue-light emitter with maximum emission at 415 nm and fluorescence quantum yield of 0.15, while solid-state PBNME film showed its emission centered at 380 nm. Furthermore, as-formed PBNME manifested favorable thermal stability and relatively high electrical conductivity of about 10⁻¹ S cm⁻¹ at room temperature.