Irina Shiyanovskaya

Self-organization of supramolecular helical dendrimers into complex electronic materials

The discovery of electrically conducting organic crystals and polymers has widened the range of potential optoelectronic materials, provided these exhibit sufficiently high charge carrier mobilities and are easy to make and process. Organic single crystals have high charge carrier mobilities but are usually impractical, whereas polymers have good processability but low mobilities. Liquid crystals exhibit mobilities approaching those of single crystals and are suitable for applications, but demanding fabrication and processing methods limit their use. Here we show that the self-assembly of fluorinated tapered dendrons can drive the formation of supramolecular liquid crystals with promising optoelectronic properties from a wide range of organic materials. We find that attaching conducting organic donor or acceptor groups to the apex of the dendrons leads to supramolecular nanometre-scale columns that contain in their cores π-stacks of donors, acceptors or donor–acceptor complexes exhibiting high charge carrier mobilities. When we use functionalized dendrons and amorphous polymers carrying compatible side groups, these co-assemble so that the polymer is incorporated in the centre of the columns through donor–acceptor interactions and exhibits enhanced charge carrier mobilities. We anticipate that this simple and versatile strategy for producing conductive π-stacks of aromatic groups, surrounded by helical dendrons, will lead to a new class of supramolecular materials suitable for electronic and optoelectronic applications.

Surface-mediated light-controlled Friedericksz transition in a nematic liquid crystal cell

Surface-mediated director reorientation in a pure nematic liquid crystal (LC) cell in the presence of both a dc and low-power optical field has been observed. A surface-dependent lowering of the Friedericksz transition voltage in a planar cell upon light irradiation was found. It is believed that this effect is due to a light-induced change in the near-surface ion concentration in the presence of a dc field and a photosensitive surface. Enrichment in the ion concentration near the surface causes a redistribution of the electric field in the cell and its localization near the surface. As a consequence, the energy of interaction between the LC and the dc field near the surface overcomes the anchoring energy and results in the director reorientation.

50.1: Distinguished Contributed Paper: Single Substrate Encapsulated Cholesteric LCDs: Coatable, Drapable and Foldable

We have developed the first ever reflective cholesteric liquid crystal displays on single textile substrates made with simple coating processes. This paper reports on a novel approach for fabrication of ultra-thin encapsulated cholesteric liquid crystal displays with transparent conducting polymers as bottom and top electrodes. These displays are fabricated from bottom-up by sequential coating of various functional layers on fabric materials. Encapsulation of the cholesteric liquid crystal droplets in polymer matrix and mechanical flexibility of the conducting polymers allow us to create durable and highly conformable textile displays. We discuss the development and status of this next generation display technology for both monochrome and multi-color cholesteric displays.

Progress in flexible and drapable reflective cholesteric displays

— Recent results from encapsulation work on the development of flexible and drapable cholesteric liquid-crystal displays (LCDs) on substrates such as thin plastics, fabrics, and even paper will be presented. The approaches used to create flexible displays using single- and dual-substrate methods based on printable emulsions and polymerization-induced phase-separation (PIPS) techniques will be discussed.

60.2: Novel Optically Addressable Photochiral Displays Erica Montbach

We show for the first time, a novel optically written bistable cholesteric display using a simple electrode structure and reversible photo addressable azo binaphthyl chiral materials. These displays are inherently high resolution, require no drive electronics and can be made flexible.

Substrate-free cholesteric liquid-crystal displays

— This paper demonstrates the first substrate-free cholesteric liquid-crystal displays. The encapsulated cholesteric displays are ultra-thin (with a total thickness around 20 μm) and ultra-lightweight (0.002 g/cm2). The displays exhibit unprecedented conformability, flexibility, and drapability while maintaining electro-optical performance and mechanical integrity. All functional display layers are sequentially coated on a preparation substrate and then lifted-off from the preparation substrate to form a free-standing display. The display fabrication process, electro-optical performance, and display flexibility are discussed.

6.4: Single Substrate Coatable Multicolor Cholesteric Liquid Crystal Displays

This paper describes new ultra-thin multicolor cholesteric liquid crystal displays with all functional layers coated sequentially on a single flexible substrate. Shared electrode driving is implemented for the first time to drive a passive matrix multicolor emulsion based displays comprising of three stacked layers of cholesteric droplets embedded in a polymer matrix.

56.1: Invited Paper: Recent Progress in Flexible and Drapable Reflective Cholesteric Displays

In this paper, we present recent results from encapsulation work in developing flexible and drapable cholesteric liquid crystal displays on substrates such as thin plastics, fabrics, and even paper. The approaches to create flexible displays with single and dual substrate methods based on printable emulsions and polymerization induced phase separation techniques will be discussed.

Erratum: Self-organization of supramolecular helical dendrimers into complex electronic materials (Nature (2002) 419 (384-387))

This corrects the article DOI: nature01072

Rugged and drapable cholesteric liquid crystal displays

We developed a novel technology for the fabrication of reflective cholesteric liquid crystal displays coatable on a single substrate using a layer-by-layer approach. Encapsulated cholesteric liquid crystals serving as an electro-optical layer and transparent conducting polymer films serving as electrodes are coated and printed on a variety of unconventional substrates, including ultra-thin plastic, paper, and textile materials to create conformable displays. The displays are capable of offering excellent electro-optical properties of the bulk cholesteric liquid crystals, including full-color, IR capability, bistability, low power, high brightness and contrast, combined with the ruggedness and pressure insensitivity of the liquid crystal droplets embedded in a polymer matrix. Durability of encapsulated cholesteric liquid crystals and single substrate approach allows for display flexing, folding, rolling and draping during image addressing without any image distortion. Our single substrate approach with natural cell-gap control significantly simplifies the fabrication process of the LCDs especially for large area displays. This paper will discuss the development, status, and merits of this novel display technology.