Ion-Conductive Nanostructured Polymer Films Formed by Photopolymerization of Lyotropic Columnar Liquid-Crystalline Monomers, Composed of a Zwitterionic Compound and a Protic Ionic Liquid

• Published in: Crystals (Basel) Vol. 10; no. 4; p. 276
• Main Authors: Cao, Siyu, Yoshio, Masafumi, Seki, Atsushi
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.04.2020
• Subjects: ion-conductive materials; ionic liquids; lyotropic liquid crystals; nanochannels; zwitterionic compounds
• DOI: 10.3390/cryst10040276
• ISSN: 2073-4352

Here, we report on a new family of columnar nanostructured polymer films forming protic nanochannels that exhibit good ionic conductivities in the order of 10−4–10−3 S cm−1 at ambient temperature. These polymer films were obtained by the in situ photopolymerization of lyotropic columnar liquid crystals, consisting of a polymerizable taper-shaped zwitterionic compound and a protic ionic liquid (imidazolium bis(trifluoromethylsulfonyl)imide), in the presence of 15 wt% water. The composition of the protic ionic liquid in the mixture was changed from 40 to 60 mol%. The ionic conductivities were measured by an alternating current impedance method. The ionic conductivity increased with the increase of the protic ionic liquid. The conductivities of columnar nanostructured polymer films were about 2–3 orders of magnitude higher than those of amorphous polymer films prepared by photopolymerization of the corresponding monomers in an isotropic liquid state. The formation of nanochannels in the polymer matrices significantly enhanced the ion conduction. The present two-component lyotropic liquid-crystalline self-assembly followed by photopolymerization is a promising approach to the development of high ion-conductive polymer membranes.