controllable structures, and macroscale photo-driven 2D and 3D mechanical
movements. Finally, the researches are summarized and the possible applications
are proposed.
Keywords
Liquid crystalline polymer · Photoresponsive liquid crystal · Liquid crystalline
block copolymer · Liquid crystalline elastomer · Supramolecular liquid crystal
Definition
Photoresponsive liquid crystalline polymers (LCPs) are one kind of advanced
functional materials with light-controllable characteristics. Typically, photoisomerizable azobenzenes or photocrosslinkable cinnamates are often used as mesogens to prepare photoresponsive LCPs and their LC properties and self-organizing
natures to be manipulated by light with suitable wavelength. In this entry, we would
introduce photoresponsive properties, the ordered structures, and potential applications of several LCPs in the form of homopolymer, block copolymer (BC),
crosslinked elastomer, and supramolecular matters.
Introduction
Liquid crystals (LCs) are a state of matter between solid and liquid, which has a
long-range ordering with fluidity as well. Friedrich Reinitzer, an Australian botanist,
first discovered the so-called the fourth state of matter. He observed two melting
points when he studied a natural product, cholesteryl benzoate, opening the gate of
the research on LCs. As one of the most fascinating soft matters, LC show unique
properties (Ikeda 2003): (1) self-organizing nature; (2) fluidity with a long-range
order; (3) cooperative motion; (4) anisotropy in all kinds of physical properties; and
(5) mesogenic alignment under external fields. These distinctive natures make it hot
in various fields including physics, chemistry, material science, biomedicine, and
other interdisciplinary fields.
Different for three-dimensional (3D) ordered crystals, LCs possess
one-dimensional (1D) or two-dimensional (2D) order. Typical phases of LCs such
as nematic, smectic, and cholesteric are given in Fig. 1. In general, nematic LC
molecules are centrosymmetric, and the nematic phase has only an orientational
order and lack of positional order. As a result, the molecules are free to flow, and
their center of mass positions are randomly distributed as in disordered liquid but
still maintain their long-range directional order. The cholesteric phase not only has
an orientational order similar to the nematic phase in all physical properties but also
has an arrangement in a helical way. The periodic distance is often called a pitch. The
smectic phases possess a positional order, and the position of the molecules is
correlated in some ordered pattern. Lamellar structures with 2D ordering can be
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X. Li and H. Yu
movements. Finally, the researches are summarized and the possible applications
are proposed.
Keywords
Liquid crystalline polymer · Photoresponsive liquid crystal · Liquid crystalline
block copolymer · Liquid crystalline elastomer · Supramolecular liquid crystal
Definition
Photoresponsive liquid crystalline polymers (LCPs) are one kind of advanced
functional materials with light-controllable characteristics. Typically, photoisomerizable azobenzenes or photocrosslinkable cinnamates are often used as mesogens to prepare photoresponsive LCPs and their LC properties and self-organizing
natures to be manipulated by light with suitable wavelength. In this entry, we would
introduce photoresponsive properties, the ordered structures, and potential applications of several LCPs in the form of homopolymer, block copolymer (BC),
crosslinked elastomer, and supramolecular matters.
Introduction
Liquid crystals (LCs) are a state of matter between solid and liquid, which has a
long-range ordering with fluidity as well. Friedrich Reinitzer, an Australian botanist,
first discovered the so-called the fourth state of matter. He observed two melting
points when he studied a natural product, cholesteryl benzoate, opening the gate of
the research on LCs. As one of the most fascinating soft matters, LC show unique
properties (Ikeda 2003): (1) self-organizing nature; (2) fluidity with a long-range
order; (3) cooperative motion; (4) anisotropy in all kinds of physical properties; and
(5) mesogenic alignment under external fields. These distinctive natures make it hot
in various fields including physics, chemistry, material science, biomedicine, and
other interdisciplinary fields.
Different for three-dimensional (3D) ordered crystals, LCs possess
one-dimensional (1D) or two-dimensional (2D) order. Typical phases of LCs such
as nematic, smectic, and cholesteric are given in Fig. 1. In general, nematic LC
molecules are centrosymmetric, and the nematic phase has only an orientational
order and lack of positional order. As a result, the molecules are free to flow, and
their center of mass positions are randomly distributed as in disordered liquid but
still maintain their long-range directional order. The cholesteric phase not only has
an orientational order similar to the nematic phase in all physical properties but also
has an arrangement in a helical way. The periodic distance is often called a pitch. The
smectic phases possess a positional order, and the position of the molecules is
correlated in some ordered pattern. Lamellar structures with 2D ordering can be
418
X. Li and H. Yu