• Journal of the Korean Chemical Society
• /
• v.42 no.3
• /
• pp.315-322
• /
• 1998

A series of new dimesogenic compounds were prepared and their thermotropic and liquid crystalline properties were studied by differential scanning calorimetry and on a hot-stage of a polarizing microscope. These compounds, 1,10-bis[2,5-bis(4-substitutedphenoxycarbonyl)phenoxy]decanes, consist of two bis(ρ-substitutedphenoxy)terephthalate units interconnected through a oxydecamethyleneoxy spacer on the central terephthaloyl units resulting in the structure of "H-shaped" dimeric twin compounds. The terminal substitutent groups were changed; X=-F, -H, -I, -Cl, -Br, $-NO_2,\;-CF_3,\;-OC_4H_9,\;-CN\;and\;-C_6H_5.$ The compounds with X=$-OC_4H_9,\;-CN\;and\;-C_6H_5$ were monotropically nematic. In contrast, the compounds with $X=-F, -H, -I, -Cl, -Br, $-NO_2\;and\;-CF_3$ were non-liquid crystals. The nematic group efficiency of these compounds was in the order of -C_6H_5>-CN>-OC_4H_9.$

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.2
• /
• pp.217-221
• /
• 2012

As a part of basic research to improve screen quality, which deteriorates when strain occurs within optical sheets in LCD modules for laptop computers, a measurement system is needed to analyze the influence of heat and moisture, which are the main factors causing the strain. It is assumed that the existence of an air gap less of than 0.5 mm inside the LCD module causes humid air from outside to permeate through the module. To investigate this phenomenon, in this study a thin printed circuit board (PCB) of compact sensors that measure temperature and humidity is inserted into LCD modules, and thus, the changes in temperature and humidity can be analyzed in real time. The results can be used as basic data for simulation of the deformation behavior and structural design of LCD modules in the future.

• Polymer(Korea)
• /
• v.34 no.4
• /
• pp.369-375
• /
• 2010

We used melt polymerization method to prepare a series of aromatic liquid crystals (LCs) based on aromatic ester and amide units with the reactive methyl-maleimide end group, and then the resulting thermally cross-linked LCs to produce LC thermoset films by means of solution casting and the followed heat treatment. The synthesized LCs and LCTs were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomechanical analysis (TMA), X-ray diffractometry (XRD), and polarizing optical microscopy (POM) with a hot stage. All of the LCs prepared by melt polymerization method formed smectic mesophases. The thermal properties of the LC and LCT films were strongly affected by the mesogen units in the main chain structures. The thermal expansion coefficients of samples were in the range of 27.72~50.95 ppm/$^{\circ}C$.

• Proceedings of the Optical Society of Korea Conference
• /
• 2006.02a
• /
• pp.197-198
• /
• 2006

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.43 no.1
• /
• pp.79-86
• /
• 2017

This study is related to a lamellar liquid crystal make-up cleansing formulation with a hologram-like unique appearance between two polarizing plates. Make-up cleansing formulations with a lamellar liquid crystal phase have been extensively studied for a long time, but there have been limitations in practical commercialization because of increasing turbidity and viscosity. In this study, to solve this problem, alkyl chains of surfactants were modified to increase the fluidity of the liquid crystal phase, and electrostatic repulsion force was increased by introducing anionic surfactant. The lamellar liquid crystal make-up cleansing formulation which introduced anionic surfactants can easily inhibit crystallization through electrostatic repulsion force, thereby showing excellent stability overtime, maintaining transparent appearance and viscosity. In addition, we have newly introduced an in vitro cleansing evaluation method using fluorescent material and in vivo imaging system (IVIS) for objective and quantitative cleansing ability evaluation. The excellent cleansing ability of lamellar liquid crystal cleansing formulation has been confirmed by newly developed evaluation method. On the other hand, when lamellar liquid crystal make-up cleansing formulation was placed between orthogonally arranged two polarizing plates, a specific pattern like a hologram can be observed. This phenomenon is presumably interpreted as the interference between the visible light passing through the liquid crystal formulation and the lamellar structure. The lamellar structure of cleansing formulation was confirmed by SAXS analysis, exhibiting Bragg spacing ratio of 1 : 2. The lamellar liquid crystal make-up cleansing formulation prepared in this study would be useful for future application in make-up cleansing due to its excellent stability, cleansing ability, and unique hologram-like pattern placed between two polarizing plates.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.41 no.4
• /
• pp.315-324
• /
• 2015

In this study, we prepared liquid crystal emulsion composed of amphiphilic substance $C_{14-22}$ alcohol, $C_{12-20}$ alkyl glucoside, behenyl alcohol and studied liquid crystal emulsion of properties and in vitro skin permeation. The results of formulation experiments, the clear liquid crystalline structure was observed in the ratio of $C_{14-22}$ alcohol 0.8%, $C_{12-20}$ alkyl glucoside 3.2%, behenyl alcohol 4% in the formulation. The results of physical property measurements, the viscosity of liquid crystal emulsion and O/W emulsion applied as a control group was respectively $1871.26{\sim}1.15Pa{\cdot}s$, $1768.69{\sim}1.14Pa{\cdot}s$ and the shear stress of O/W emulsion was 178.68 ~ 909.18 Pa, that of liquid crystal emulsion was 190.45 ~ 919.38 Pa. The storage modulus of O/W emulsion was 3428.53 ~ 9157.45 Pa, that of liquid crystal emulsion was 4487.82 ~ 8195.59 Pa. The tan (delta) value of O/W emulsion which means a ratio of viscosity to elasticity was 0.43 ~ 0.19, and that of liquid crystal emulsion was 0.23 ~ 0.25. The water content value on the skin for liquid crystal emulsion was significantly higher from 1 h to 6 h compared with that of O/W emulsion and the transepidermal water loss on the skin was significantly superior in skin moisture loss suppression from 30 min to 4 h compared with that of O/W emulsion. The results of skin permeation using glycyrrhizic acid, the result of skin permeation amount of liquid crystal emulsion for 24 h was $64.58{\mu}g/cm^2$, that of O/W emulsion was $37.07{\mu}g/cm^2$, that of butylene glycol solution was $41.05{\mu}g/cm^2$. Hourly permeability results, it is showed that skin penetration effect of the liquid crystal emulsion increases after 8 h. These results suggest that liquid crystal emulsions are effective for skin moisturizing effect and function as potential efficacy ingredient delivery system for the transdermal delivery.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.47 no.1
• /
• pp.85-92
• /
• 2021

The stratum corneum is formed from keratinocytes and intercellular lipids, with ceramide as the main component of intercellular lipids. Ceramides are one of the important components of the intercellular lipids to form a lamellar structure, but they are insoluble and therefore are not suitable for direct application to the skin. Thus, it was intended to apply ceramide to the formulation of pluronic lecithin organogel (PLO gel), which received constant attention among drug delivery systems. A suitable oil for formulation was selected and a PLO gel containing ceramide was manufactured. Liquid crystal formation and variation were observed using polarized microscopes, and viscoelastic analysis was performed to find out the viscoelastic behavior of the PLO gel. Small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) analysis were performed to confirm the structures in the formulation. Results showed that the size and stability of the liquid crystal differed depending on the content ratio of ceramide and lecithin in the PLO gel containing ceramide. Furthermore, viscoelastic analysis showed the stability of the formulation, and SAXS/WAXS analysis confirmed that the PLO gel without ceramide had hexagonal structure of the quadrilateral system array, and the PLO gel with ceramide had the lamellar structure of the quadrilateral system array.

• Applied Chemistry for Engineering
• /
• v.26 no.6
• /
• pp.698-705
• /
• 2015

Two series of symmetric dimesogenic compounds containing a butylene or 1-methylbutylene spacer as a flexible group were synthesized. The mesogenic groups of synthesized compounds consist of an azobenzene group with a terminal substituent. Chemical structures as well as, thermal, mesomorphic, and photochemical properties of the synthesized compounds were investigated using FT-IR, $^1H-NMR$, differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and UV-visible spectrometry. P-H, P-F, and $P-OC_6H_{13}$ showed monotropic liquid crystal phases, whereas the others showed enantiotropic liquid crystal phases. Compounds with butylene group as a flexible spacer exhibited wider mesophase temperature ranges and higher thermal transition temperatures than compounds containing a 1-methylbutylene group. Compounds with a high absolute value of the Hammett substituent constant exhibited high thermal transition temperatures and improved stability in the liquid crystal phase. Furthermore, in the absence or presence of UV light illumination, terminal substituents of the azomesogenic group were important factors in deciding the maximum absorbance wavelength (${\lambda}_{max}$) and the rate of photoisomerization (K).

• Polymer(Korea)
• /
• v.28 no.1
• /
• pp.41-50
• /
• 2004

A new hydroxypropyl chitosan capable of forming a thermotropic liquid crystalline phase and two kinds of derivatives based on the hydroxypropyl chitosan (6-cholesteryloxycarbonylpentoxypropyl) chitosans (CHPCTs) and acrylic acid esters of CHPCT (CHPCTEs) were synthesized. The crosslinked films with liquid crystalline order were also prepared by photocrosslinking CHPCTE in mesophase. The liquid crystalline properties for all the samples and the swelling behavior of the crosslinked samples in acetone were investigated. In contrast with the hydroxypropyl chitosan, all the uncrosslinked cholesteryl-bearing samples farmed monotropic cholesteric phases with left-handed helicoidal structures and exhibited reflection colors over the full cholesteric range. This is the first report of a thermotropic cholesteric liquid crystalline chitosan derivative with reflection bands in the visible region. Both the optical pitches (λ$\_$m/'S) of CHPCT and CHPCTE decrease with temperature or with cholesteryl content at a given temperature. However, the λ$\_$m/ of CHPCT was larger than that of CHPCTE at the same temperature and at the same cholesteryl content. All the crosslinked samples did not display reflection colors, indicating that the cholesteric structure of CHPCTE significantly changes upon crosslinking. The two-dimentional anisotropic swelling characteristic of liquid crystalline networks was observed for all the crosslinked samples.

• Polymer(Korea)
• /
• v.30 no.5
• /
• pp.422-425
• /
• 2006

Due to their periodic helical structure, cholesteric liquid crystals (CLC) have a unique ability to selectively reflect visible light. CLC films reflecting a broad wavelength band were prepared by inducing a pitch gradient in CLC layers through a diffusion of small molecules and through a thermal mixing of cyclic siloxane CLC molecules with different pitch lengths. Various pitch gradients in the CLC cell were observed using UV/Vis spectrometer and SEM technique.