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Nematic Liquid Crystal on a Two Dimensional Hexagonal Lattice and its Application.

Arslan Shehzad M, Hoang Tien D, Waqas Iqbal M, Eom J, Park JH, Hwang C, Seo Y - Sci Rep (2015)

Bottom Line: From the experimental data, it was found that there were 6 different alignment orientations of the liquid crystal molecules on a single crystal substrate.We explain this result considering the bending of the tail of the liquid crystal molecules.Using this anchoring effect with six accurate discrete angles, a novel non-volatile display can be developed with micron-scale pixel size, due to the molecular level accuracy of the alignment.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Nanotechnology &Advanced Materials, HMC, and GRI, Sejong University, Seoul 143-747, South Korea.

ABSTRACT
We have studied the alignment of liquid crystal adsorbed onto graphene and hexagonal boron nitride by using a polarized optical microscope. From the experimental data, it was found that there were 6 different alignment orientations of the liquid crystal molecules on a single crystal substrate. This result has never been reported and is quite different from other previous results. As the hexagonal lattice has a threefold rotational symmetry, three different alignment orientations were expected, but our result seems counter-intuitive. We explain this result considering the bending of the tail of the liquid crystal molecules. Using this anchoring effect with six accurate discrete angles, a novel non-volatile display can be developed with micron-scale pixel size, due to the molecular level accuracy of the alignment.

No MeSH data available.


Thermal stability of liquid crystal on HOPG.(a) POM image was obtained after LC was deposited on HOPG. (b) Sample was heated above the clearing transition temperature (33 °C), and POM image became dark, confirming LC was in isotropic phase. (c) After it was cooled again, most LC molecules were aligned with the original shapes of domains, but interestingly some of domains was created or annihilated, as pointed by arrows.
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f5: Thermal stability of liquid crystal on HOPG.(a) POM image was obtained after LC was deposited on HOPG. (b) Sample was heated above the clearing transition temperature (33 °C), and POM image became dark, confirming LC was in isotropic phase. (c) After it was cooled again, most LC molecules were aligned with the original shapes of domains, but interestingly some of domains was created or annihilated, as pointed by arrows.

Mentions: The thermal stability of LC between graphite and rubbed layer was studied. A sandwich structure cell was fabricated with a 5 μm gap and was filled with LC by capillary action. When sample was heated (60 °C) above the isotropic transition temperature, the POM image revealed dark color due to the random orientation of liquid crystal (Fig. 5(b)). Then, it was cooled down to the nematic phase again. Different background colors between the images before (Fig. 5(a)) and after (Fig. 5(c)) heating is due to the slight change of the thickness of LC. It was observed that most LC domains were recovered, confirming the anchoring orientation of LCs on graphite surface was not reoriented during the thermal treatment. However, the arrows in the Fig. 5 indicate an exception where the domain boundary was moved, and domains disappeared and were generated during the thermal cycle. This indicates that the aligning direction of the LC molecules was not strictly determined by the morphological structure of the substrate, but the LC molecules have freedom to change their anchoring orientation to a certain degree.


Nematic Liquid Crystal on a Two Dimensional Hexagonal Lattice and its Application.

Arslan Shehzad M, Hoang Tien D, Waqas Iqbal M, Eom J, Park JH, Hwang C, Seo Y - Sci Rep (2015)

Thermal stability of liquid crystal on HOPG.(a) POM image was obtained after LC was deposited on HOPG. (b) Sample was heated above the clearing transition temperature (33 °C), and POM image became dark, confirming LC was in isotropic phase. (c) After it was cooled again, most LC molecules were aligned with the original shapes of domains, but interestingly some of domains was created or annihilated, as pointed by arrows.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4542626&req=5

f5: Thermal stability of liquid crystal on HOPG.(a) POM image was obtained after LC was deposited on HOPG. (b) Sample was heated above the clearing transition temperature (33 °C), and POM image became dark, confirming LC was in isotropic phase. (c) After it was cooled again, most LC molecules were aligned with the original shapes of domains, but interestingly some of domains was created or annihilated, as pointed by arrows.
Mentions: The thermal stability of LC between graphite and rubbed layer was studied. A sandwich structure cell was fabricated with a 5 μm gap and was filled with LC by capillary action. When sample was heated (60 °C) above the isotropic transition temperature, the POM image revealed dark color due to the random orientation of liquid crystal (Fig. 5(b)). Then, it was cooled down to the nematic phase again. Different background colors between the images before (Fig. 5(a)) and after (Fig. 5(c)) heating is due to the slight change of the thickness of LC. It was observed that most LC domains were recovered, confirming the anchoring orientation of LCs on graphite surface was not reoriented during the thermal treatment. However, the arrows in the Fig. 5 indicate an exception where the domain boundary was moved, and domains disappeared and were generated during the thermal cycle. This indicates that the aligning direction of the LC molecules was not strictly determined by the morphological structure of the substrate, but the LC molecules have freedom to change their anchoring orientation to a certain degree.

Bottom Line: From the experimental data, it was found that there were 6 different alignment orientations of the liquid crystal molecules on a single crystal substrate.We explain this result considering the bending of the tail of the liquid crystal molecules.Using this anchoring effect with six accurate discrete angles, a novel non-volatile display can be developed with micron-scale pixel size, due to the molecular level accuracy of the alignment.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Nanotechnology &Advanced Materials, HMC, and GRI, Sejong University, Seoul 143-747, South Korea.

ABSTRACT
We have studied the alignment of liquid crystal adsorbed onto graphene and hexagonal boron nitride by using a polarized optical microscope. From the experimental data, it was found that there were 6 different alignment orientations of the liquid crystal molecules on a single crystal substrate. This result has never been reported and is quite different from other previous results. As the hexagonal lattice has a threefold rotational symmetry, three different alignment orientations were expected, but our result seems counter-intuitive. We explain this result considering the bending of the tail of the liquid crystal molecules. Using this anchoring effect with six accurate discrete angles, a novel non-volatile display can be developed with micron-scale pixel size, due to the molecular level accuracy of the alignment.

No MeSH data available.