Definition
Liquid crystallinity in rigid or semirigid polymers emerges in sufficiently concentrated solutions (lyotropic) or at sufficiently low temperatures (thermotropics); some
liquid crystal polymers exhibit both thermotropic and lyotropic behavior. The key
characteristics of liquid crystalline polymers such as self-assembly, packing, defects,
functionalities, and processability are discussed. Liquid crystalline polymers (LCPs)
are found in industrial applications, technology, and throughout nature and their
theoretical and computational characterization as presented in this chapter serves as a
basis for process and material innovation in synthetic and biological materials.
Introduction
Liquid Crystals
Liquid crystals (LCs) are anisotropic viscoelastic mesophases with partial degrees of
orientational and positional order (Rey 2007, 2009, 2010; Rey and Herrera-Valencia
2012; Rey et al. 2014). LCs where symmetry breaking transitions are driven by
changes in temperature are known as thermotropic liquid crystals (TLC), whereas in
those where changes in concentration trigger transitions are considered as lyotropic
liquid crystals (LLC) (Chandrasekhar 1992; de Gennes and Prost 1993; Larson
1999; Donald et al. 2006). Some materials such as chromonic liquid crystals exhibit
both behaviors. Amphiphilic molecules are another type of mesogen capable of selfassembling into lamellar, cubic, or even bi-continuous phases, which are not
discussed here but the reader is referred to Rey (2007, 2009, 2010), Rey and
Herrera-Valencia (2012), and references therein for a complete overview. LCs are
classified as soft matter materials that exhibit a large and usually nonlinear response
when submitted to weak forces and also show slow and non-instantaneous response
exhibiting nonequilibrium dynamics as a consequence whose response or characteristic times can be up to one billion times slower than those from ordinary liquids
exhibiting non-Newtonian and complex viscoelastic behavior (Chandrasekhar 1992;
de Gennes and Prost 1993; Larson 1999; Doi 2013). In addition, these soft mesophases exhibit defects and textures as hard anisotropic materials, with disclinations
and dislocations walls, whose origin is due to frustration or incompatibility in the
orientation of the material (Chandrasekhar 1992; de Gennes and Prost 1993; Rey and
Denn 2002; Rey and Herrera-Valencia 2012; Rey et al. 2014). Liquid crystallinity
emerges in anisodiametric molecules, such as flat discs or rod-like molecules that can
self-assemble into phases, that exhibit only orientational order such as the nematic
phase or other phases where not only this ordering is present but also 1D positional
order, such as the smectic A phase that can be built-up with achiral rods or disc
columns. When chirality is present at the molecular level or when a chiral dopant is
added to a nematic phase for instance, a chiral nematic phase is obtained
(denominated also as cholesteric). The ordering of such phase is that of a nematic
10 Liquid Crystalline Polymers: Structure and Dynamics
275
Liquid crystallinity in rigid or semirigid polymers emerges in sufficiently concentrated solutions (lyotropic) or at sufficiently low temperatures (thermotropics); some
liquid crystal polymers exhibit both thermotropic and lyotropic behavior. The key
characteristics of liquid crystalline polymers such as self-assembly, packing, defects,
functionalities, and processability are discussed. Liquid crystalline polymers (LCPs)
are found in industrial applications, technology, and throughout nature and their
theoretical and computational characterization as presented in this chapter serves as a
basis for process and material innovation in synthetic and biological materials.
Introduction
Liquid Crystals
Liquid crystals (LCs) are anisotropic viscoelastic mesophases with partial degrees of
orientational and positional order (Rey 2007, 2009, 2010; Rey and Herrera-Valencia
2012; Rey et al. 2014). LCs where symmetry breaking transitions are driven by
changes in temperature are known as thermotropic liquid crystals (TLC), whereas in
those where changes in concentration trigger transitions are considered as lyotropic
liquid crystals (LLC) (Chandrasekhar 1992; de Gennes and Prost 1993; Larson
1999; Donald et al. 2006). Some materials such as chromonic liquid crystals exhibit
both behaviors. Amphiphilic molecules are another type of mesogen capable of selfassembling into lamellar, cubic, or even bi-continuous phases, which are not
discussed here but the reader is referred to Rey (2007, 2009, 2010), Rey and
Herrera-Valencia (2012), and references therein for a complete overview. LCs are
classified as soft matter materials that exhibit a large and usually nonlinear response
when submitted to weak forces and also show slow and non-instantaneous response
exhibiting nonequilibrium dynamics as a consequence whose response or characteristic times can be up to one billion times slower than those from ordinary liquids
exhibiting non-Newtonian and complex viscoelastic behavior (Chandrasekhar 1992;
de Gennes and Prost 1993; Larson 1999; Doi 2013). In addition, these soft mesophases exhibit defects and textures as hard anisotropic materials, with disclinations
and dislocations walls, whose origin is due to frustration or incompatibility in the
orientation of the material (Chandrasekhar 1992; de Gennes and Prost 1993; Rey and
Denn 2002; Rey and Herrera-Valencia 2012; Rey et al. 2014). Liquid crystallinity
emerges in anisodiametric molecules, such as flat discs or rod-like molecules that can
self-assemble into phases, that exhibit only orientational order such as the nematic
phase or other phases where not only this ordering is present but also 1D positional
order, such as the smectic A phase that can be built-up with achiral rods or disc
columns. When chirality is present at the molecular level or when a chiral dopant is
added to a nematic phase for instance, a chiral nematic phase is obtained
(denominated also as cholesteric). The ordering of such phase is that of a nematic
10 Liquid Crystalline Polymers: Structure and Dynamics
275