Functional Liquid-Crystalline Polymers for Ionic and Electronic Conduction - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 151

Fig. 1 Nano-segregated structures formed by self-assembly of LC molecules: OD 0-dimen-
sional micellar cubic, 1 D hexagonal columnar, 2 D lamellar or smectic, and 3 D bicontinu-
ous cubic
In this review, we will focus on ion- and electron-conductive thermotropic
LC polymers and oligomers. A variety of mesomorphic structures has been
constructed utilizing non-covalent interactions, which influences ionic and
electronic carrier transport processes.
2
Ion-Conductive Liquid-Crystalline Polymers
2.1
Organic Ion-Conductive Polymers
The development of high performance electrolytes is an important task in the
production of devices for electric energy storage and delivery such as lithium
ion batteries, capacitors, and electrochromic devices. Carbonate-based mate-
rials are one of the liquid electrolytes. Carbonate-based liquid electrolytes are
now commonly used for the economical lithium ion batteries [31]. The so-
lution of carbonate and lithium salts exhibits high ionic conductivity, on the
order of 10 -3 Scm -1 at ambient temperature.
The recent development of electrolytes is directed to the replacement of
liquid electrolytes with solvent-free polymer electrolytes [32-36]. Polymer
electrolytes have advantages as electrolytes because of their flexibility, light-
ness, easy processability, and safety. The complexes of poly(ethylene oxide)s
(PEOs) with lithium salts have been intensively studied as solid polymer
electrolytes since 1975 when Wright found that PEOs can be used as ion-
conductive materials in such systems [37]. These polymers can operate both
as separators that keep the distance between electrodes, and as electrolytes
that lead to the production of batteries having overall polymer structures.
Lithium cation dissolved in PEOs is stabilized by the ion-dipole interac-
tions between lithium cations and the lone pairs of oxygen atoms in the PEO
chains. The ions are conducted by the segmental motions of the ethylene
oxide chains. A variety of PEO-based polymers, such as comb-shaped poly-
mers containing highly mobile oligo(ethylene oxide) side chains [38], were
prepared for the development of higher ion-conductive materials. However,