Keywords
Crosslinked liquid crystalline polymers · Photoresponsive · Deformation ·
Photochemical phase transition · Photothermal effect · Actuators
Definition
Crosslinked liquid crystalline polymers (CLCPs) are a type of promising smart materials that possess both the ordered alignment of liquid crystals (LCs) and the elasticity of
polymer networks. The anisotropic photodeformation of CLCPs takes place when
mesogens experience order to disorder change in response to light. Therefore, many
actuators are fabricated from CLCPs and have potential applications in artificial
muscles, micro-optomechanical systems, optics, and energy-harvesting fields.
Introduction
Smart materials have drawn wide attention recently due to their unique properties and
are potential for applications in artificial muscles and soft actuators, biomedical systems,
etc. Among these smart materials, CLCPs appear to be especially attractive because of
their superior characteristics combining the order of LCs and the excellent mechanical
properties arising from polymer networks. Because the mesogens tend to show alignment in CLCPs coupled with the elastic property of the polymer networks, the CLCPs as
three-dimensional networks are able to undergo controllable and reversible deformation
due to the alignment change induced by external stimuli. Compared to other stimulusdriven method, such as heat, pressure, pH variations, electric field, and magnetic field,
light is a particularly ideal stimulus, since it is a clean energy and can be precisely and
conveniently manipulated in terms of wavelength, intensity, and polarization direction.
The incorporation of photoresponsive chromophores into CLCPs can provide photoresponsiveness and induce a reduction in LC alignment upon exposure to UV light as a
result of photochemical reaction (Ikeda et al. 2007; Ube and Ikeda 2014; White and
Broer 2015). Therefore, photodeformable CLCPs can convert light energy into mechanical actuation directly and definitely merit further investigation.
In this chapter, we mainly describe photoinduced deformation observed in CLCPs.
The mechanisms of deformation based on photochemical phase transition and photothermal effect are also included. Our goal is to summarize the developments of
photoinduced behavior of CLCPs and provide an introduction on their potential applications as light-driven devices as well as recent progress in this field.
Photodeformation Based on Photochemical Phase Transition
Cooperative motion of molecules in LC phases may be most advantageous in
changing the molecular alignment by external stimuli. The alignment of the majority
of LC molecules will be changed if the alignment of a small portion of LC molecules
362
L. Qin et al.
Crosslinked liquid crystalline polymers · Photoresponsive · Deformation ·
Photochemical phase transition · Photothermal effect · Actuators
Definition
Crosslinked liquid crystalline polymers (CLCPs) are a type of promising smart materials that possess both the ordered alignment of liquid crystals (LCs) and the elasticity of
polymer networks. The anisotropic photodeformation of CLCPs takes place when
mesogens experience order to disorder change in response to light. Therefore, many
actuators are fabricated from CLCPs and have potential applications in artificial
muscles, micro-optomechanical systems, optics, and energy-harvesting fields.
Introduction
Smart materials have drawn wide attention recently due to their unique properties and
are potential for applications in artificial muscles and soft actuators, biomedical systems,
etc. Among these smart materials, CLCPs appear to be especially attractive because of
their superior characteristics combining the order of LCs and the excellent mechanical
properties arising from polymer networks. Because the mesogens tend to show alignment in CLCPs coupled with the elastic property of the polymer networks, the CLCPs as
three-dimensional networks are able to undergo controllable and reversible deformation
due to the alignment change induced by external stimuli. Compared to other stimulusdriven method, such as heat, pressure, pH variations, electric field, and magnetic field,
light is a particularly ideal stimulus, since it is a clean energy and can be precisely and
conveniently manipulated in terms of wavelength, intensity, and polarization direction.
The incorporation of photoresponsive chromophores into CLCPs can provide photoresponsiveness and induce a reduction in LC alignment upon exposure to UV light as a
result of photochemical reaction (Ikeda et al. 2007; Ube and Ikeda 2014; White and
Broer 2015). Therefore, photodeformable CLCPs can convert light energy into mechanical actuation directly and definitely merit further investigation.
In this chapter, we mainly describe photoinduced deformation observed in CLCPs.
The mechanisms of deformation based on photochemical phase transition and photothermal effect are also included. Our goal is to summarize the developments of
photoinduced behavior of CLCPs and provide an introduction on their potential applications as light-driven devices as well as recent progress in this field.
Photodeformation Based on Photochemical Phase Transition
Cooperative motion of molecules in LC phases may be most advantageous in
changing the molecular alignment by external stimuli. The alignment of the majority
of LC molecules will be changed if the alignment of a small portion of LC molecules
362
L. Qin et al.