Nanoparticle-Liquid Crystalline Elastomer Composites
Under photoactive LCE, the nanoparticle composite of LCE needs discussion as this
system provides a new stimulant for actuation. The combination of suitable nanoparticles with LCEs makes multi-controlled actuation system responsive to various
stimuli such as electric and magnetic fields and broad-spectrum light. On the other
hand, the strengthening effect, due to nanoparticle dispersion in LCE, may dampen
the actuation properties. This prompted study at very low level of nanoparticle
modification, which was found to be very successful.
Both MWNTs and SWNTs are known to absorb light efficiently in the visible
as well as near-IR range and convert the absorbed energy into heat. Both acting as
nanoscale heating source change photo-energy into heat. If the heat produced is
transferred efficiently throughout the matrix, the LC-isotropic phase transition can
be triggered easily, leading to a shape change in the LCE nanocomposite film.
Being nanoparticle, the percolation threshold can be attained at very low concentration. Such a network can, effectively, serve as a thermal conduction pathway
due to the high thermal conductivity of the SWNTs. Heat can be delivered
throughout the LCE matrix uniformly and rapidly when irradiated with IR light
source. The temperature of the matrix can increase much above the nematicisotropic transition temperature in very short time. White light also shows similar
response. In addition to visible and IR light, CNTs also show absorption in
microwave and terahertz and megahertz frequency ranges.
The presence of noble metal nanoparticle (NP) in PDLC microstructure leads to
one interesting observation. It is possible to create surface plasmon excitations
(Hinojosa and Sharma 2010) at the NP-polymer interface which influences the
electro-optical properties of PDLCs. Due to ferroelectric nanoparticles like BaTiO 3
inclusion, the electro-optical properties of liquid crystal cells is observed as the local
electric fields builds up (Darla et al. 2014).
Photoresponsive Main-Chain Oligomers
The properties and functions of polymers/oligomers depend on chain length and
chemical structures. However, the polymers/oligomers synthesized by common
methods are polydisperse in nature. Thus, the dependence of physical properties
on the chain length and chemical structure cannot be measured correctly. Exact
polymers/oligomers containing azo-functional groups is done by synthetic
approach using acyclic diene metathesis (ADMET) technique, which allows the
introduction of azobenzenes into olefin structures repetitively for the generation of
saturated and unsaturated azo oligomers (Appiah et al. 2017). The azo oligomers
exhibit molecular weight-dependent growth with time. The aggregate sizes of
saturated azo-oligomers are bigger than their unsaturated counterparts, and also
the growth of the former is more rapid than the latter. The hydrodynamic radius of
the micelles decreases by approximately 14% during UV irradiation because of the
increased polarity induced by isomerization of the azobenzene from its planar
410
A. B. Samui
Under photoactive LCE, the nanoparticle composite of LCE needs discussion as this
system provides a new stimulant for actuation. The combination of suitable nanoparticles with LCEs makes multi-controlled actuation system responsive to various
stimuli such as electric and magnetic fields and broad-spectrum light. On the other
hand, the strengthening effect, due to nanoparticle dispersion in LCE, may dampen
the actuation properties. This prompted study at very low level of nanoparticle
modification, which was found to be very successful.
Both MWNTs and SWNTs are known to absorb light efficiently in the visible
as well as near-IR range and convert the absorbed energy into heat. Both acting as
nanoscale heating source change photo-energy into heat. If the heat produced is
transferred efficiently throughout the matrix, the LC-isotropic phase transition can
be triggered easily, leading to a shape change in the LCE nanocomposite film.
Being nanoparticle, the percolation threshold can be attained at very low concentration. Such a network can, effectively, serve as a thermal conduction pathway
due to the high thermal conductivity of the SWNTs. Heat can be delivered
throughout the LCE matrix uniformly and rapidly when irradiated with IR light
source. The temperature of the matrix can increase much above the nematicisotropic transition temperature in very short time. White light also shows similar
response. In addition to visible and IR light, CNTs also show absorption in
microwave and terahertz and megahertz frequency ranges.
The presence of noble metal nanoparticle (NP) in PDLC microstructure leads to
one interesting observation. It is possible to create surface plasmon excitations
(Hinojosa and Sharma 2010) at the NP-polymer interface which influences the
electro-optical properties of PDLCs. Due to ferroelectric nanoparticles like BaTiO 3
inclusion, the electro-optical properties of liquid crystal cells is observed as the local
electric fields builds up (Darla et al. 2014).
Photoresponsive Main-Chain Oligomers
The properties and functions of polymers/oligomers depend on chain length and
chemical structures. However, the polymers/oligomers synthesized by common
methods are polydisperse in nature. Thus, the dependence of physical properties
on the chain length and chemical structure cannot be measured correctly. Exact
polymers/oligomers containing azo-functional groups is done by synthetic
approach using acyclic diene metathesis (ADMET) technique, which allows the
introduction of azobenzenes into olefin structures repetitively for the generation of
saturated and unsaturated azo oligomers (Appiah et al. 2017). The azo oligomers
exhibit molecular weight-dependent growth with time. The aggregate sizes of
saturated azo-oligomers are bigger than their unsaturated counterparts, and also
the growth of the former is more rapid than the latter. The hydrodynamic radius of
the micelles decreases by approximately 14% during UV irradiation because of the
increased polarity induced by isomerization of the azobenzene from its planar
410
A. B. Samui