Following Sharpless' visionary characterization of several idealized reactions as click reactions, the materials science and synthetic chemistry communities have pursued numerous routes toward the identification and implementation of these click reactions. Herein, we review the radical-mediated thiol-ene reaction as one such click reaction. This reaction has all the desirable features of a click reaction, being highly efficient, simple to execute with no side products and proceeding rapidly to high yield. Further, the thiol-ene reaction is most frequently photoinitiated, particularly for photopolymerizations resulting in highly uniform polymer networks, promoting unique capabilities related to spatial and temporal control of the click reaction. The reaction mechanism and its implementation in various synthetic methodologies, biofunctionalization, surface and polymer modification, and polymerization are all reviewed.

Thiol–Ene Click Chemistry

Micromachining technology was used to prepare chemical analysis systems on glass chips (1 centimeter by 2 centimeters or larger) that utilize electroosmotic pumping to drive fluid flow and electrophoretic separation to distinguish sample components. Capillaries 1 to 10 centimeters long etched in the glass (cross section, 10 micrometers by 30 micrometers) allow for capillary electrophoresis-based separations of amino acids with up to 75,000 theoretical plates in about 15 seconds, and separations of about 600 plates can be effected within 4 seconds. Sample treatment steps within a manifold of intersecting capillaries were demonstrated for a simple sample dilution process. Manipulation of the applied voltages controlled the directions of fluid flow within the manifold. The principles demonstrated in this study can be used to develop a miniaturized system for sample handling and separation with no moving parts.

Micromachining a miniaturized capillary electrophoresis-based chemical analysis system on a chip

Polymers for flexible displays: From material selection to device applications

An overview is given of theory and experiments on liquid crystal phases which appear in solutions of elongated colloidal particles or stiff polymers. The Onsager (1949) virial thecry for the isotropionematic transition of thin rodlike particles is treated comprehensively along with extensions to polydisperse solutions and soft interactions. Computer simulations of liquid crystal phases in hard particle fluids are summarized and used to assess the quality of statistical mechanical thwries for stiff panicles at higher dume haion-like the inclusion of higher Virial coefficients, yexpansion, scaled particle theory and density functional theory. Both computer simulations and density functional theory indicate formation of more highly ordered smectic phases. The range of experimental applicability h strongly widened by the extension of the viriai theory to wormlike chains by Khokhlov and Semenov (1981, 1982). Fmally, experimental results for a number of carefully studied, charged and uncharged colloids and polymers are summarized and wmpared to theoretical results. IE many cases the agreement is semi-quantitative.

/pdf/phase-transitions-in-lyotropic-colloidal-and-polymer-liquid-23qsyytblc.pdf

Phase transitions in lyotropic colloidal and polymer liquid crystals

The English-language dictionary defines wrinkles as "small furrows, ridges, or creases on a normally smooth surface, caused by crumpling, folding, or shrinking". In this paper we review the scientific aspects of wrinkling and the related phenomenon of buckling. Specifically, we discuss how and why wrinkles/buckles form in various materials. We also describe several examples from everyday life, which demonstrate that wrinkling or buckling is indeed a commonplace phenomenon that spans a multitude of length scales. We will emphasize that wrinkling is not always a frustrating feature (e.g., wrinkles in human skin), as it can help to assemble new structures, understand important physical phenomena, and even assist in characterizing chief material properties.

Soft matter with hard skin : From skin wrinkles to templating and material characterization

Inverse twisted nematic display with self-aligned 4-domain on surface relief photopolymer

The poling dynamics and relaxation process in PVDF/PMMA blends are studied with the second harmonic generation (SHG) and birefringence measurements in order to determine the temporal stabilities and temperature dependences. The Maker fringe and the phase modulation methods were used for studing the SHG and optical birefringence measurements, respectively. Both the birefringence and the SHG intensity increase during the poling process in the same fashion. The relaxation process of the sample whose polar order increases with poling is studied with the SHG at several poling temperatures. Both the poling and the relaxation processes exhibit a form of the stretched exponential behavior with different characteristic times.

Birefringence and second harmonic generation in PVDF/PMMA blends

We report on a wide viewing liquid crystal display with bi-level microstructures fabricated at ambient temperature through an imprinting process which is simple and versatile. Hemispherical microstructures and rectangular microstructures, made of a photopolymer through a single-step imprinting process, produce multi-domains of the liquid crystal (LC) for enhancing the viewing property and provide spacers for maintaining the uniform cell gap, respectively. Our LC cell with embossed bi-level microstructures shows symmetric viewing properties in a wide range of polar angles, contrast ratio of 100:1, and the response time of 34 ms.

http://mipd.snu.ac.kr/Admin/thesis/vw_bilevel_%28MCLC09_09%29.pdf

Wide Viewing Liquid Crystal Displays with Bi-level Surface Microstructures Fabricated by an Imprinting Method

A phase modulation technique using a photoelastic modulator is employed for measuring the optical retardation as a function of temperature in the whole range of the nematic state. The surface parameters are determined self-consistently from both the capacitance and the phase retardation of the nematic liquid crystal. It is found that the surface anchoring energy is on the order of 1.0 erg/cm2 at room temperature.

Temperature Dependence of Anisotropic Surface Anchorage of Nematic Liquid Crystals

The liquid crystal(LC) display is the most promising technology of the flat panel displays covering all applications from small mobile to large television applications. To understand the operating principles and improve the performances of the various LC displays, one should grasp the anisotropic nature of the LC and the propagation of light in the anisotropic media. Basic formulas governing the distribution of the LC molecules, directly related to the electro-optic effects of the LC devices, are described in view of the macroscopic interaction. Based on the matrix representation, the polarization analysis for the LC devices is also presented.

/pdf/fundamentals-of-liquid-crystal-and-liquid-crystal-optics-10x88cleg5.pdf

Sin-Doo Lee

Papers

Inverse twisted nematic display with self-aligned 4-domain on surface relief photopolymer

Birefringence and second harmonic generation in PVDF/PMMA blends

Wide Viewing Liquid Crystal Displays with Bi-level Surface Microstructures Fabricated by an Imprinting Method

Temperature Dependence of Anisotropic Surface Anchorage of Nematic Liquid Crystals

Fundamentals of Liquid Crystal and Liquid Crystal Optics