the highly oriented nematic solution is coagulated in the water bath. It is
established that during the process of coagulation, the alignment of the nematic
phase remains frozen in the coagulation bath, which ultimately helps in the
development of highly ordered fibers with an order parameter of about 0.95 as
explained earlier. The order parameter of the solution can be directly controlled
either by changing the concentration of the polymer solution or by modification
of the temperature. The temperature under consideration is found to be the
temperature of the water present in the coagulation bath. As a result of a high
degree of order, these fibers exhibit highly anisotropic behavior showing Young’s
modulus of about 100 GPa and lateral modulus of about 1.8 GPa as reported
(Picken 1996).
Special Class of Liquid Crystalline Polymers: Liquid Crystalline
Elastomers
The scientific publication related to liquid crystalline elastomer is on the development of crosslinked polysiloxane with mesogen side groups (Gleim and Finkelmann
1989; Sánchez-Ferrer et al. 2009). Liquid crystalline elastomers show a combination
of properties of an elastomer and a liquid crystal. Hence, this kind of material
exhibits high molecular mobility with anisotropic properties specific for liquid
crystalline phases. They exhibit rubbery elastic properties with weakly crosslinked
polymer networks. This combination of properties makes this class of material
attractive in microengineering field. Temperature, light, and voltages are the
governing forces that may generate movements via a change in the order in the
structure of liquid crystals. The elastomer films are stretchable up to 150% in a
microdevice and can move up to 400 times its mass owing to nematic and isotropic
transition (Kato and Tanabe 2009). Liquid crystalline elastomers are used in microsystems for the fabrication of microactuators, for example, valve, switch, etc., and
specifically in artificial muscles.
Liquid crystal elastomers are mainly based on polysiloxane or polysiloxane-based
materials with liquid crystals chemically bonded to polysiloxane backbone. One of
the specific features of liquid crystal elastomer is the presence of liquid crystalline
monodomain. This kind of structural formation results when a mechanical field is
applied to the nematic elastomer. In this respect, the polydomain of liquid crystalline
elastomer is converted to a monodomain state, where every mesogen unit is arranged
parallel to each other resulting in director orientation. This kind of material has
potential in optical fields such as contact lenses, piezoelectric sensors, and ferroelectric materials. Liquid crystalline elastomers with main- and side-chain LCPs in a
small amount of mesogens form smectic C mesophase, where the domains have
permanent dipole moments leading to piezoelectric properties (Papadopoulos et al.
2010). Liquid crystalline elastomers are also utilized in soft electrochemical actuators
for frequencies less than kilohertz range and at a temperature in the range of glass
transition to smectic to isotropic transition temperature (White and Broer 2015).
1 Introduction to Liquid Crystalline Polymers
21
established that during the process of coagulation, the alignment of the nematic
phase remains frozen in the coagulation bath, which ultimately helps in the
development of highly ordered fibers with an order parameter of about 0.95 as
explained earlier. The order parameter of the solution can be directly controlled
either by changing the concentration of the polymer solution or by modification
of the temperature. The temperature under consideration is found to be the
temperature of the water present in the coagulation bath. As a result of a high
degree of order, these fibers exhibit highly anisotropic behavior showing Young’s
modulus of about 100 GPa and lateral modulus of about 1.8 GPa as reported
(Picken 1996).
Special Class of Liquid Crystalline Polymers: Liquid Crystalline
Elastomers
The scientific publication related to liquid crystalline elastomer is on the development of crosslinked polysiloxane with mesogen side groups (Gleim and Finkelmann
1989; Sánchez-Ferrer et al. 2009). Liquid crystalline elastomers show a combination
of properties of an elastomer and a liquid crystal. Hence, this kind of material
exhibits high molecular mobility with anisotropic properties specific for liquid
crystalline phases. They exhibit rubbery elastic properties with weakly crosslinked
polymer networks. This combination of properties makes this class of material
attractive in microengineering field. Temperature, light, and voltages are the
governing forces that may generate movements via a change in the order in the
structure of liquid crystals. The elastomer films are stretchable up to 150% in a
microdevice and can move up to 400 times its mass owing to nematic and isotropic
transition (Kato and Tanabe 2009). Liquid crystalline elastomers are used in microsystems for the fabrication of microactuators, for example, valve, switch, etc., and
specifically in artificial muscles.
Liquid crystal elastomers are mainly based on polysiloxane or polysiloxane-based
materials with liquid crystals chemically bonded to polysiloxane backbone. One of
the specific features of liquid crystal elastomer is the presence of liquid crystalline
monodomain. This kind of structural formation results when a mechanical field is
applied to the nematic elastomer. In this respect, the polydomain of liquid crystalline
elastomer is converted to a monodomain state, where every mesogen unit is arranged
parallel to each other resulting in director orientation. This kind of material has
potential in optical fields such as contact lenses, piezoelectric sensors, and ferroelectric materials. Liquid crystalline elastomers with main- and side-chain LCPs in a
small amount of mesogens form smectic C mesophase, where the domains have
permanent dipole moments leading to piezoelectric properties (Papadopoulos et al.
2010). Liquid crystalline elastomers are also utilized in soft electrochemical actuators
for frequencies less than kilohertz range and at a temperature in the range of glass
transition to smectic to isotropic transition temperature (White and Broer 2015).
1 Introduction to Liquid Crystalline Polymers
21