Molecular Order Imprint Polymerization of Furan–Thiophene-Based Monomers with Electrochemical Polymerization in Chiral Liquid Crystals

A polymerization reaction in chiral liquid crystal produced electro-optically active polymers from achiral furan–thiophene-based monomers. The set of polymers prepared in this study had characteristics of liquid crystal molecular order and organic semiconductors. The optically active aromatic copolymers were synthesized via an electrochemical method in cholesteric liquid crystals (Ch-LCs). Electrical properties and chirality can be tuned to choose suitable monomer units. The polymers obtained were evaluated by polarizing optical microscopy (POM), circular dichroism, UV–vis spectroscopy, cyclic voltammetry, reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. POM observations of the products showed a vortex-type fingerprint texture. Polymerization of the monomers containing only two active polymerization sites produced the resultant compounds with good transcription of the fingerprint texture and chirality from the Ch-LC electrolyte solution. The membrane-forming behavior can be improved by introducing furans at the edges of monomers. The absorption bands derived from polarons and bipolarons as charge carriers of conducting polymers can be tuned by an electrical redox process and hydrazine vaporization treatment. Electrical control for the optical activity of the furan–thiophene-based polymers was achieved

Preparation of helical liquid crystal electrolyte with L-isoleucine derivatives and molecular asymmetric imprinting polymerization in liquid crystal to produce electro-optically coloration active polymers having chiral charge carrier chiralions

Molecular asymmetric imprinting polymerization in the cholesteric liquid crystal was carried out. An L-isoleucine derivative with fluorine was synthesized for a chiral inducer to induce the cholesteric liquid crystal from the nematic liquid crystal. A substance with multiple asymmetric centers can be obtained conveniently to use amino acid as chiral substance. The L-isoleucine derivative induced helical structure for 4-cyano-4'-hexylbiphenyl (6CB). Electrochemical preparation of π-conjugated polymers was carried out in the cholesteric liquid crystal. Fingerprint texture derived from the cholesteric liquid crystal was transcribed to the polymers. UV-vis and circular dichroism (CD) spectra of oxidized (doped) for and reduced (dedoped) form of the polymer were measured. Electrochemical polymerization in the helical liquid crystal produced the molecular aggregation imprinted chiral polymers, which have liquid crystal-like aggregation form, chirality with no stereogenic center via formation of polymer atropisomer, and electrochemical driven change in optical activity, as a form of electro-optically coloration active polymers. Finally, the polarons and bipolarons are in the form of chiral structure. These charge carriers in the polymers can be determined as chiral charge carrier “chiralions”.</p

Optically Electroactive Polymer Synthesized in a Liquid Crystal with Cyclosporin ACircularly Polarized Electron Spin Resonance

Cyclosporine A (CsA), a naturally derived biomaterial and physiologically active substance, is commonly used as an immunosuppressant. In this study, CsA was revealed to function as a chiral inducer of cholesteric liquid crystals (CLCs) with a high helical twisting power. CsA induced helical structures in 4-cyano-4′-pentylbiphenyl, a synthetic liquid crystal (LC) used for general purposes. Electrochemical polymerization in CLC with CsA was also performed. The polymer prepared in CLC showed electro-optical activity via chiral induction by CsA. Synchrotron X-ray diffraction measurements indicated that the polymer film prepared in the CLC formed in the manner of LC molecular arrangement through molecular form imprinting from the LC order, although the polymer exhibited no liquid crystallinity. The polymer showed structural color and laser light oscillation diffraction derived from its periodic structure. The anisotropy of the circularly polarized electron spin resonance signals for the resulting polymer with respect to the magnetic field was observed

Synthesis of conductive polymer alloys by electrochemical polymerization in chiral liquid crystal

Synthesis of conjugated polymer alloys with chirality was developed. Optically active polymer alloys were prepared by electrochemical polymerization in cholesteric liquid crystal. First, we prepared polymer alloys with 2,2′-bithiophene (BT) and bis-(3,4-ethylenedioxythiophene) as monomers. By mixing the amounts of the two types of monomers, surface structure and optical texture were tuned. Next, we prepared polymer alloys with the monomers by electrochemical polymerization. The electrochemical redox function was present in all the polymer alloys. The absorption bands derived from electrochemical doping and dedoping were observed in an oxidized and reduced state. Circular dichroism (CD) of the polymer alloys was controllable with electrochemical redox tuning. The CD bands in the near-IR range were assigned to the doping band as a form of polarons (radical cations). This research examined electrochemical control of charge carrier “chiralions.” Synchrotron XRD measurement confirmed the molecular form imprinting of the polymer alloys from the host cholesteric liquid crystal.</p