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.

Azobenzene is one of the most famous photoresponsive chromophores, and it repeatedly photoisomerizes. In this study, main-chain type polyazobenzenes bearing chiral substituents in the side-chain are synthesized by the Suzuki–Miyaura coupling method. The chiral aggregation process of main-chain type polyazobenzene is investigated. Then, intermolecular interaction of these polymers allows the formation of chiral aggregates as higher order structures. Trans-to-cis photoisomerization of the polymers was confirmed with in situ UV–vis absorption spectra. Development of π-conjugation in the backbone can be an important factor in the design of main-chain type azobenzene polymers. In addition, we induced light-driven changes in the chiroptical activity. The microstructure of the polymers is examined with synchrotron radiation X-ray diffraction and a technique to define “chiral photochromism”.

Azobenzene switches its structure instantaneously by reversible trans‐to‐cis and cis‐to‐trans photoisomerization with light irradiations. Dynamic change in polymer structure is expected via introducing an azobenzene unit into the main chain. In this study, a set of methyl‐substituted azobenzene–carbazole conjugated copolymers is synthesized by the Suzuki–Miyaura coupling method. Introduction of methyl substituents to the azobenzene unit of the monomer, and polymerization in a high‐boiling solvent improve the molecular weight of the polymer. Decrease of effective conjugation length due to the twisted structure of the main chain allows progress of photoisomerization. The microstructure of the polymer was determined with grazing incidence X‐ray diffraction (GIXD) measurements using synchrotron radiation. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1756–1764

In this short communication, we report a new carbon material prepared from meta-linked polyaniline that exhibits weak antiferromagnetic interactions at low temperature. The synthesis of poly(meta-aniline), abbreviated as m-PANI, was conducted using the Ullmann reaction with the aid of Cu+ as a catalyst in the presence of K2CO3. After the generation of radical cations by vapor-phase doping with iodine, carbonization was performed to prepare carbon polyaniline (C-PANI), which comprises condensed benzene rings. Analysis with a superconducting quantum interference device revealed that the resultant carbon exhibits antiferromagnetism at low temperatures. The discovery of this weak antiferromagnetic carbon may contribute to the development of carbon magnets.

While only a few studies have investigated the synthesis of main chain-type polyazobenzenes, they continue to draw an increasing amount of attention owing to their industrial applications in holography, dyes, and functional adhesives. In this study, dibromoazobenzene was prepared as a monomer for constructing azo-based π-conjugated polymers. Miyaura–Suzuki cross-coupling polymerization was conducted to develop copolymers containing an azobenzene unit as a photoisomerization block and a pyrimidine-based liquid crystal generator block. The prepared polymers exhibited thermotropic liquid crystallinity and underwent cis and trans photoisomerization upon irradiation with ultraviolet and visible light. Furthermore, the photoisomerization behavior was examined using optical absorption spectroscopy and synchrotron X-ray diffraction spectrometry.