it offers advantages when dealing with the structural properties as is the rigidity of
the molecule (Donald et al. 2006; Rey 2007, 2009, 2010). In general terms, it is more
likely to form nematic phases rather than isotropic ones when the molecules present
stiffness. On the other hand, crystallinity in the polymer, favored with molecular
stiffness, must be decreased to a certain degree in order to profit from the fluid-like
behavior (Larson 1999). In lyotropics, crystallinity is reduced without losing molecular stiffness with the addition of solvent; on the other hand, flexible spacers are
generally introduced in the molecular backbone to reduce crystallinity in thermotropics. Nonetheless, they also reduce the molecular stiffness leading to semiflexible
chains with persistence length less than the molecular length (Larson 1999; Donald
et al. 2006).
Main-Chain and Side-Chain Liquid Crystalline Polymers
Depending on the location of the rigid or semirigid units in the polymeric mesogens
(PMs), they can be classified as main-chain or side-chain (Larson 1999; Donald et al.
2006) as the name suggests the former are those where the rigid units are part of the
backbone of the molecule, whereas the latter units are part of the ramifications. A
combination of these two is also possible (Larson 1999; Donald et al. 2006; Rey
2007, 2009, 2010; Herrera-Valencia 2012; Rey et al. 2014). As a part of the family of
LCs in general, a schematic classification is given in Fig. 1 to highlight the position
of the main-chain, side-chain, and even elastomers; such classification is given in
terms of their molecular components such as: (i) rods, (ii) discs, (iii) amphiphiles,
and spheres.
Main-Chain Liquid Crystalline Polymers
Main-chain structural polymers are characterized by their high strength, high precision moldings, and are used extensively in the electronics industry with applications
ranging from computer connectors to casings for mobile phones. Medical applications are also being developed (Larson 1999; Donald et al. 2006). In a fiber form,
liquid crystalline polymers have been used into fabrics for high endurance sails and
were used as air bags that cushioned the landing of NASA’s highly successful
missions to Mars (Larson 1999; Donald et al. 2006).
Side-Chain Liquid Crystalline Polymer
The anisotropic units are attached to a flexible backbone, usually via flexible spacers
in side-chain LCPs (Larson 1999; Donald et al. 2006). Such flexible spacers may be
incorporated between the mesogenic groups to give a single linear molecule (Donald
et al. 2006); or a flexible polymer chain can be used as a backbone to which the
mesogenic sections are added as side groups where the connections are often made
10 Liquid Crystalline Polymers: Structure and Dynamics
277
the molecule (Donald et al. 2006; Rey 2007, 2009, 2010). In general terms, it is more
likely to form nematic phases rather than isotropic ones when the molecules present
stiffness. On the other hand, crystallinity in the polymer, favored with molecular
stiffness, must be decreased to a certain degree in order to profit from the fluid-like
behavior (Larson 1999). In lyotropics, crystallinity is reduced without losing molecular stiffness with the addition of solvent; on the other hand, flexible spacers are
generally introduced in the molecular backbone to reduce crystallinity in thermotropics. Nonetheless, they also reduce the molecular stiffness leading to semiflexible
chains with persistence length less than the molecular length (Larson 1999; Donald
et al. 2006).
Main-Chain and Side-Chain Liquid Crystalline Polymers
Depending on the location of the rigid or semirigid units in the polymeric mesogens
(PMs), they can be classified as main-chain or side-chain (Larson 1999; Donald et al.
2006) as the name suggests the former are those where the rigid units are part of the
backbone of the molecule, whereas the latter units are part of the ramifications. A
combination of these two is also possible (Larson 1999; Donald et al. 2006; Rey
2007, 2009, 2010; Herrera-Valencia 2012; Rey et al. 2014). As a part of the family of
LCs in general, a schematic classification is given in Fig. 1 to highlight the position
of the main-chain, side-chain, and even elastomers; such classification is given in
terms of their molecular components such as: (i) rods, (ii) discs, (iii) amphiphiles,
and spheres.
Main-Chain Liquid Crystalline Polymers
Main-chain structural polymers are characterized by their high strength, high precision moldings, and are used extensively in the electronics industry with applications
ranging from computer connectors to casings for mobile phones. Medical applications are also being developed (Larson 1999; Donald et al. 2006). In a fiber form,
liquid crystalline polymers have been used into fabrics for high endurance sails and
were used as air bags that cushioned the landing of NASA’s highly successful
missions to Mars (Larson 1999; Donald et al. 2006).
Side-Chain Liquid Crystalline Polymer
The anisotropic units are attached to a flexible backbone, usually via flexible spacers
in side-chain LCPs (Larson 1999; Donald et al. 2006). Such flexible spacers may be
incorporated between the mesogenic groups to give a single linear molecule (Donald
et al. 2006); or a flexible polymer chain can be used as a backbone to which the
mesogenic sections are added as side groups where the connections are often made
10 Liquid Crystalline Polymers: Structure and Dynamics
277