Biomedical Engineering Reference
In-Depth Information
Among several other unique properties that ionic DLCs may display is electronic
and anisotropic ionic conduction. However, a detailed comprehensive account of
existing reports and systematic investigation on ionic DLCs is limited because of
their ot en complex synthesis, characterization and tedious purii cation steps. h is
chapter presents an overview of recent advances in the chemistry of ionic DLCs
with a particular focus on their ionic self-assembly that are useful for the prepara-
tion of new low-dimensionally functional sot solid materials. h e fundamental
phenomenon underlying the approach to electrical conductors is addressed in this
chapter using nanomaterials (such as carbon nanotubes) and ionic DLCs that have
great potential to orient the nanomaterials for anisotropic electrical conduction.
h e mesomorphic behavior of ionic DLCs (including oligomers and polymers) is
described with a particular focus directed towards the development of fundamen-
tal understanding of structural-mesophase morphology relationship. Meticulous
attention is given to the dependence of mesomorphism on the inl uence of spacer
length, counter ions, location and types of the charged groups in determining the
supramolecular organization of these compounds. Finally, some concluding per-
spectives are presented related to optical, electronic and other properties such as
their use in certain biological functions, catalysis and templates for new organic
synthesis.
Keywords:
Liquid crystals, discotic, columnar, conductivity, ionic, lyotropic,
thermotropic
9.1 Introduction
Over the last 30 years, since the early work of Chandrasekhar and his
coworkers [1], there has been a growing interest in a distinct family of liq-
uid crystals (LCs), the so-called discotic liquid crystals (DLCs). Discotic
liquid crystals represent a broad, well-understood class of sot matter which
possess the ability to self-organize into highly anisotropic and ordered
structures such as columns that function not only as organic anisotropic
semiconductors [2-4], but which may also contribute to the development
of new smart materials for directional ion conductivity and charge trans-
port if combined with suitable ionic liquids. h is combination (ionic liquids
and DLCs) has opened up a new possibility of organic molten salts in mate-
rials science, leading to a new subi eld of DLCs, the so-called ionic DLCs.
h ey not only exhibit l uid ordered states but also function as anisotropic
organic semiconductors that ei ciently conduct ions. However, a detailed
comprehensive account of existing reports and systematic investigation on
ionic DLCs is limited because of their ot en complex synthesis, character-
ization and tedious purii cation steps. h is chapter presents an overview
of recent advances in the chemistry of ionic DLCs, with a particular focus
