Electroluminescent liquid crystals polymers

M. Grell, D.D.C. Bradley, M. Inbasekaran, and E.P. Woo, A glass-forming conjugated main-chain liquid crystal polymer for polarized electroluminescence applications, Adv. Mater., 9 798-802, 1997. 

High-resolution circuitry and active devices employing Langmuir-Blodgett film techniques or polymer-based transistors are being considered for the sophisticated electronics required in future vehicles. Temperature or energy balance in the vehicle could be controlled through conductive polymers or semiconductor deposits on electrochromic windows. Electroluminescent liquid crystals and fluorescent and electrochromic materials used for visual displays show promise for future development. 

Monomers of die type Aa B. are used in step-growth polymerization to produce a variety of polymer architectures, including stars, dendrimers, and hyperbranched polymers.26 28 The unique architecture imparts properties distinctly different from linear polymers of similar compositions. These materials are finding applications in areas such as resin modification, micelles and encapsulation, liquid crystals, pharmaceuticals, catalysis, electroluminescent devices, and analytical chemistry. 

Aromatic compounds have not only been of academic interest ever since organic chemistry became a scientific discipline in the first half of the nineteenth century but they are also important products in numerous hydrocarbon technologies, e.g. the catalytic hydrocracking of petroleum to produce gasoline, pyrolytic processes used in the formation of lower olefins and soot or the carbonization of coal in coke production [1]. The structures of benzene and polycyclic aromatic hydrocarbons (PAHs) can be found in many industrial products such as polymers [2], specialized dyes and luminescence materials [3], liquid crystals and other mesogenic materials [4]. Furthermore, the intrinsic (electronic) properties of aromatic compounds promoted their use in the design of organic conductors [5], solar cells [6],photo- and electroluminescent devices [3,7], optically active polymers [8], non-linear optical (NLO) materials [9], and in many other fields of research. 

Moreover, organic functionalization of a polymer chain can lead to improvement in the physical properties, such as thermal stability and mechanical strength of the resulting siloxanes (Figure 3.1). Appropriate substitution on the polysiloxane backbone can lead to diverse materials such as liquid crystals," crosslinking agents, conductive and electroluminescent polymers, nonlinear optical materials,and bactericides. ... 

The photoluminescence of polyaniline has been studied as a function of the polymer redox state. It was stated that each of the three PANI species have fluorescent emissions with different quantum yields. When conductive domains are present, the emission fi-om excitons located either inside these domains or near to them is efficiently quenched [40], Organic electroluminescent devices (LED s) are a possible alternative to liquid crystal displays and cathodic tubes, especially for the development of large displays. The principal setup for a polymeric LED is ITO/light-emitting polymer/metal. A thin ITO electrode on a transparent glass or polymeric substrate serves as the anode, while metals such as Al, Ca or Mg are used as cathode materials. After applying an electric field, electrons and holes are injected into the polymer. The formation of e /h" " pairs leads to the emission of photons. One of most important opportunities to follow from the use of poly-... 

The present 10 volume handbook has a much broader scope. It includes semiconductor materials, quantum wells and quantum dots, liquid crystals, conducting polymers, laser materids, photoconductors, electroluminescent and photorefractive materials, nanostructured, supramolecular, and self-assembled materials, ferroelectrics, and superconductors. Applications of these materials in photoconductors, optical fibers, xerography, solar cells, dynamic random access memory, and sensors are described. The Handbook contains contributions by 180 leading experts from 25 different countries. It truly represents the worldwide research efforts and results that support the global market of optoelectronics. All scientific and technical workers in this broad field are indebted to the contributing authors, the editor and Academic Press for publishing this comprehensive handbook for the new millennium. It will support further growth in a field that already has surpassed my wildest expectations of 40 years ago. 

New phosphorus containing polysulfones could be obtained by using different phosphorus containing diols in the classical synthesis of PSF (Scheme 6.4). Diols can contain phosphorus in main chain position or incorporate in a phenanthrene-type ring as side chain. These different phosphorus-containing diols form aromatic polyethers by polycondensation with dihalogen-substituted aromatic sulfones [48]. The chain structure of the polymer (aromatic or aliphatic) and the position of phosphorus in the chain influence the polymer properties (electroluminescence [49,50], flame retardancy [51], liquid crystal properties [52]). 

Aldred, M.R, et al. Organic electroluminescence using polymer networks firom smectic liquid crystals. Liq. Cryst. 33(4), 459-467 (2006)... 

There have been a number of attempts to make OLEDs based on discotic liquid crystals although performance is disappointing probably because of aggregation. Wendorff and co-workers demonstrated monoesters of triphenylene 7, see Table 6.2, in their Colp phase and mainchain polymers of triphenylene in the Coin phase in electroluminescent devices. High electric fields were required, 10 V cm , and the lifetimes of the devices are probably not very long [40,41]. The bilayer devices made by Bock and co-workers, e.g., ITO/triphenylene 8 (hole transporter)/perylene 9 (electron transporter)/aluminium [43,44] exploit materials that have liquid crystal phases above room temperature [42, 43]. Simple variants on these structures were synthesised, which had green, blue and sometimes almost white light emission [44]. 

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