Helical Spin Polymer with Magneto-Electro-Optical Activity

A chiral π-conjugated polymer bearing a stable radical side group was synthesized by electrochemical polymerization in a cholesteric liquid crystal. The polymer thus obtained shows paramagnetism as well as electro- and optical activity. The polymer exhibits a one-handed helical spin order owing to the one-handed helix of the main chain and the stable radical side groups. This helical spin order endows the polymer with magneto-optical activity. In situ optical absorption and circular dichroism (CD) measurements during cyclic voltammetry analysis were used to investigate the electroactive chirality of the polymer. Optically active polarons (radical cations) as charge carriers were observed by CD and electron-spin resonance (ESR) measurements. Furthermore, the optical ellipticity of the polarons was found to be tunable using an electric field. The ESR analysis showed that the g-value of the phenoxy radicals on the polymer is 2.00403, whereas the g-value of the polarons in the main chain is 2.0025, indicating that the phenoxy radical side groups are independent of the polarons in terms of magnetic behavior. CD spectroscopy measurements revealed that the phenoxy radicals exist in a chiral environment. Thus, we successfully obtained a chiral magnetic conjugated polymer using liquid crystal imprinting polymerization. This method is a new approach for the preparation of chiral organic magnets