Jee-Hyun Ryu

The influence of nematic liquid crystal content on the electro-optical properties of a polymer dispersed liquid crystal prepared with monodisperse liquid crystal microcapsules

Highly monodisperse poly(methylmethacrylate) (PMMA)/liquid crystal (LC) microcapsules were prepared by the solute codiffusion method (SCM). In SCM, the solvency of the dispersion medium and the swelling temperature were controlled to ensure complete swelling of the LC into the PMMA substrate particles. After the solvent evaporation procedure, mononuclear LC domains were formed in every particle, and overall the LC microcapsules maintained a spherical shape, monodispersity and smooth surface. PDLC cells prepared using the LC microcapsules exhibited an excellent contrast ratio and transmittance. By increasing the LC content in these LC microcapsules, the electro-optical properties of PDLC cells have been greatly improved.

Non‐invasive Transdermal Delivery Route Using Electrostatically Interactive Biocompatible Nanocapsules

This study was supported by a grant of the Korea Health 21 R&D Project, Ministry of Health & Welfare, Republic of Korea (03-PJ1-PG1-CH14-0001).

Preparation of cholesteric liquid crystal microcapsules for application in colour image storage media

Cholesteric liquid crystal (CLC) microcapsules for application in image storage media can be obtained via a diffusion-controlled polymerization method (DPM). To improve the swelling of the CLC seed particle, in poly(methylmethacrylate) (PMMA), a polymerizable acrylate based on a cholesterol moiety was synthesized and copolymerized with MMA to prepare the seed particle. As a result, monodispersed and CLC core/shell-structured microcapsules may be obtained. The resulting CLC microcapsules selectively, absorbed visible light at around 660 nm, and so appeared blue in the mesophase. Polymer dispersed cholesteric liquid crystal (PDCLC) cells were prepared using the CLC microcapsules, and were used as an image storage medium in reversible writing/erasing experiments.

SYNTHESIS OF WATER-SOLUBLE URETHANE ACRYLATE CATIONOMERS AND THEIR ULTRAVIOLET COATING PROPERTIES

Water-soluble urethane acrylate cationomers were synthesized by incorporating N-methyldiethanolamine (MDEA) into the molecular backbone for an application of ultraviolet (UV) curing. It was found that they were easily dissolved in, because of the sufficient hydration ability of the incorporated cationic groups. Differing from conventional urethane acrylate derivatives, when UV-cured, the films of the urethane acrylate cationomers showed significantly improved coating properties. This was because of the formation of the ionic hard domains in the urethane acrylate network. In dynamic mechanical analysis (DMA), the formation of the ionic hard domain could be confirmed by detecting the glass transition peak Tgh, around 23.4°C. The dyeing of the urethane acrylate cationomer films was considerably favorable because of their positively-charged network structure.

WATER-SOLUBLE URETHANE ACRYLATE IONOMERS AND THEIR ULTRAVIOLET (UV) CURING: PREVENTION OF MOISTURE ABSORPTION

Water-soluble and ultraviolet (UV)-curable urethane acrylate ionomers containing α,α-dimethylolpropionic acid (DMPA) were synthesized varying the molecular weight of the soft segment. In addition, their coating properties were also examined. When placed in the atmosphere for a long period, the tensile strength and the initial modulus of the UV-cured ionomer films decreased. Moreover, the disappearance of the ionic hard domains was observed by the dynamic mechanical analysis (DMA). These results indicated that the strong hydrophilicity of the ionomer network readily absorbed moisture in the atmosphere. However, by changing the stoichiometric mixing ratio of the urethane acrylate ionomer to the urethane acrylate not containing ionic groups, the moisture absorption of the ionomer network was successfully prevented. In DMA measurements, it was observed that the ionic hard domains did not disappear even in a comparatively long aging time (about 3 weeks). This could be achieved by the incorporation of the hydro...