cells from damage caused by UV-induced reactive intermediates. Also, the
nanocapsule-based film/coatings can be used in packaging to increase the shelf
life of perishable substances.
Photoresponsive Membranes
Smart membranes are being used in many advanced fields of biotechnology, including drug delivery, biosensing, microfluidics, light-powered molecular machines,
molecular shuttles, data storage, etc. The responsive polymer membranes sense the
changes in their environment acting as a stimulus and make desired response, either
a controlled porosity or a texture. The chemical compositions are linked with
properties, such as pH-, ionic strength-, thermo-, light-, electric-, and magneticresponse and molecular-recognition.
Nanoporous LC networks can be used as nanoporous membranes, which are
controlled by using stimuli so that the nanopore dimensions are varied. Azobenzene
changes the dimension during isomerization from trans to cis isomer and vice versa.
Thus, its incorporation in a host molecule can vary the pore dimension that will
control the selectivity toward different size molecules. Gas permeation LC membranes can switch between an impermeable ordered state and a permeable disordered
state (Glowacki et al. 2010), while azobenzene-containing smectic LCs exhibit
anisotropic ion conduction and photoswitchable ion conduction (Nardele et al. 2015).
As an example, a photoresponsive nanoporous LC materials is made by
using azobenzene cross-linker for the hydrogen-bonded smectic liquid crystalline
polymer network (van Kuringen et al. 2015). The nanopores are created by treating
the polymer network with a base leading to the breakup of the hydrogen bonds.
During exposure to light, the lamellar spacing decreases due to the trans-cis
isomerization that alters the pore size. In fact, after UV irradiation the d-spacing
decreases due to change in molecular length of the azobenzene cross-linker during
exposure.
Future Directions
The photoactive liquid crystalline polymers have ventured in to almost all areas of
technology. The smart materials responding to various forms of trigger have great
future as the coupling with nanoparticles is the booster. The photoactive elastomer
has the ability to combine many nano-/micromachines which on combination can be
great smart force for practical purposes. Photoresponsive microcapsules and membranes provide new dimension toward ready application areas. The work on photoactive LC polymers for conversion of photo energy to electrical one has to be done
for adding to ready energy need. Bio-related photoactive LC may also be a future
direction.
414
A. B. Samui
nanocapsule-based film/coatings can be used in packaging to increase the shelf
life of perishable substances.
Photoresponsive Membranes
Smart membranes are being used in many advanced fields of biotechnology, including drug delivery, biosensing, microfluidics, light-powered molecular machines,
molecular shuttles, data storage, etc. The responsive polymer membranes sense the
changes in their environment acting as a stimulus and make desired response, either
a controlled porosity or a texture. The chemical compositions are linked with
properties, such as pH-, ionic strength-, thermo-, light-, electric-, and magneticresponse and molecular-recognition.
Nanoporous LC networks can be used as nanoporous membranes, which are
controlled by using stimuli so that the nanopore dimensions are varied. Azobenzene
changes the dimension during isomerization from trans to cis isomer and vice versa.
Thus, its incorporation in a host molecule can vary the pore dimension that will
control the selectivity toward different size molecules. Gas permeation LC membranes can switch between an impermeable ordered state and a permeable disordered
state (Glowacki et al. 2010), while azobenzene-containing smectic LCs exhibit
anisotropic ion conduction and photoswitchable ion conduction (Nardele et al. 2015).
As an example, a photoresponsive nanoporous LC materials is made by
using azobenzene cross-linker for the hydrogen-bonded smectic liquid crystalline
polymer network (van Kuringen et al. 2015). The nanopores are created by treating
the polymer network with a base leading to the breakup of the hydrogen bonds.
During exposure to light, the lamellar spacing decreases due to the trans-cis
isomerization that alters the pore size. In fact, after UV irradiation the d-spacing
decreases due to change in molecular length of the azobenzene cross-linker during
exposure.
Future Directions
The photoactive liquid crystalline polymers have ventured in to almost all areas of
technology. The smart materials responding to various forms of trigger have great
future as the coupling with nanoparticles is the booster. The photoactive elastomer
has the ability to combine many nano-/micromachines which on combination can be
great smart force for practical purposes. Photoresponsive microcapsules and membranes provide new dimension toward ready application areas. The work on photoactive LC polymers for conversion of photo energy to electrical one has to be done
for adding to ready energy need. Bio-related photoactive LC may also be a future
direction.
414
A. B. Samui