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

摘要

Five chiral inducers were synthesized with l-borneol and benzenecarboxylic acids. These chiral inducers have the same substituent (bornyl ester) but different geometries. Para-substituted chiral inducer (I-p) shows relatively high macroscopic helical twisting power (βM), while ortho-substituted chiral inducer (I-o) shows lower. This difference is related with the geometric similarity between the chiral inducers and the host liquid crystals. The result also suggested that distortion of π system induced by polar solvents causes low βM of the I-o. Optically active poly(3,4-ethylenedioxythiophene) (PEDOT) films were chemically prepared in cholesteric liquid crystal (CLC) electrolyte solution induced by the chiral inducers. Circular dichroism (CD) intensities of the resultant polymer films are almost proportional to helical twisting power (HTP) of the chiral inducers. Optical rotatory dispersion (ORD) spectra of the polymer film prepared in the CLC electrolyte induced by I-p (PF-para) shows isosbestic point during the oxidation. This indicates that electro-chiroptically active polymer film was obtained through chiral induction of the bornyl chiral inducer.