Chapter 7
Liquid Crystals
7.1 Classification
7.1.1 Thermotropic Versus Lyotropic
Liquid crystal, in a broad sense, is liquid having structures. Usually, the structure
induces the anisotropy, which is the basis for its numerous applications, such as
an LC display. Liquid crystals are often classified into two groups of thermotropic
and lyotropic. The underlying mechanism bringing them about has been regarded
as much different: Excluded volume effect and microphase separation. The thermotropic liquid crystal appears upon temperature variation. Liquid crystals of this
type can be a neat compound. Their formation comes from strong shape anisotropy of
molecules, one of the characteristics of systems consisting of not independent atoms
but molecules. The formation of thermotropic liquid crystals is understood within
a unified view of the melting of molecular crystals, as described in Chap. 6. On the
other hand, the lyotropic liquid crystal appears in multicomponent systems like a
concentrated aqueous solution of soap. Internal structures result from microphase
separation. There is no doubt that each mechanism solely works well in some liquid
crystals. Both kinds of liquid crystals exhibit various phases of different structures.
This chapter mainly concerns with the thermotropic liquid crystals (except the last
section). However, it is noteworthy that the distinction between thermotropic and
lyotropic liquid crystals is not so clear in real systems, as will be discussed later in
Sect. 9.4.4.2.
© The Editor(s) (if applicable) and The Author(s), under exclusive license
to Springer Nature Singapore Pte Ltd. 2020
K. Saito, Chemical Physics of Molecular Condensed Matter,
Lecture Notes in Chemistry 104,
https://doi.org/10.1007/978-981-15-9023-8_7
143
Liquid Crystals
7.1 Classification
7.1.1 Thermotropic Versus Lyotropic
Liquid crystal, in a broad sense, is liquid having structures. Usually, the structure
induces the anisotropy, which is the basis for its numerous applications, such as
an LC display. Liquid crystals are often classified into two groups of thermotropic
and lyotropic. The underlying mechanism bringing them about has been regarded
as much different: Excluded volume effect and microphase separation. The thermotropic liquid crystal appears upon temperature variation. Liquid crystals of this
type can be a neat compound. Their formation comes from strong shape anisotropy of
molecules, one of the characteristics of systems consisting of not independent atoms
but molecules. The formation of thermotropic liquid crystals is understood within
a unified view of the melting of molecular crystals, as described in Chap. 6. On the
other hand, the lyotropic liquid crystal appears in multicomponent systems like a
concentrated aqueous solution of soap. Internal structures result from microphase
separation. There is no doubt that each mechanism solely works well in some liquid
crystals. Both kinds of liquid crystals exhibit various phases of different structures.
This chapter mainly concerns with the thermotropic liquid crystals (except the last
section). However, it is noteworthy that the distinction between thermotropic and
lyotropic liquid crystals is not so clear in real systems, as will be discussed later in
Sect. 9.4.4.2.
© The Editor(s) (if applicable) and The Author(s), under exclusive license
to Springer Nature Singapore Pte Ltd. 2020
K. Saito, Chemical Physics of Molecular Condensed Matter,
Lecture Notes in Chemistry 104,
https://doi.org/10.1007/978-981-15-9023-8_7
143