Side-chain liquid crystalline polyesters for optical information storage

Azobenzene side-chain liquid crystalline polyester structures suitable for permanent optical storage are described. The synthesis and characterization of the polyesters together with differential scanning calorimetry and X-ray investigations are discussed. Optical anisotropic investigations and holographic storage in one particular polyester are described in detail and polarized Fourier transform infrared spectroscopic data complementing the optical data are presented. Optical and atomic force microscope investigations point to a laser-induced aggregation as responsible for permanent optical storage.     

Liquid crystals for holographic optical data storage

A tutorial review is presented to inform and inspire the reader to develop and integrate strong scientific links between liquid crystals and holographic data storage, from a materials scientist's viewpoint. The principle of holographic data storage as a means of providing a solution to the information storage demands of the 21st century is detailed. Holography is a small subset of the much larger field of optical data storage and similarly, the diversity of materials used for optical data storage is enormous. The theory of polarisation holography which produces holograms of constant intensity, is discussed. Polymeric liquid crystals play an important role in the development of materials for holographic storage and photoresponsive materials based on azobenzene are targeted for discussion due to their ease of photo-reversion between trans- and cis-states. Although the final polymer may not be liquid crystalline, irradiation can induce ordered domains. The mesogens act in a co-operative manner, enhancing refractive indices and birefringences. Surface relief gratings are discussed as a consequence of holographic storage. Cholesteric polymers comprising azobenzene are briefly highlighted. Irradiation causing cis-trans-isomerisation can be used to control helix pitch. A brief mention of liquid crystals is also made since these materials may be of future interest since they are optically transparent and amenable to photo-induced anisotropy.     

Recent developments in the supramolecular chemistry of terpyridine-metal complexes

This critical review describes recent developments in the field of supramolecular chemistry of terpyridine-metal complexes. The synthesis and characteristics of single as well as multiple homo- and heterometallic complexes is discussed. Furthermore, complexes containing fullerenes, biological building blocks, extended aggregates of different architectures as well as rings are presented. A special emphasis is placed upon the properties (e.g. redox properties, luminescence etc.) of functional systems. Potential applications in optical nano-devices, molecular storage units, molecular switches and solar cells are discussed.     

Relationship between infrared intensity theories: Electro-optical parameters and bond polar parameters

Mathematical and physical aspects are analysed of the relationship between two theoretical formulations of infrared band intensities employing parameters associated with chemical bonds: the valence optical theory and the bond polar parameters method. Parallel applications of the two theories in analysing experimental IR intensity data for H₂O and CH₃Cl are presented. The relationships of the two theoretical approaches with the atomic polar tensors theory are discussed.     

Polymers for electrical and optical data storage

Polymers possess great significance in data storage technology. Taking as an example electrical and optical data storage, the state of development, properties required and opportunities for application of selected polymers are discussed, namely: (i) ferroelectric polymers with low switching voltages and extremely short switching times for electric data storage; and (ii) transparent polymers with low birefringence and high thermal stability for optical data storage. In the area of electrical data storage devices/memories, ferroelectric polymers have not been able to establish themselves up to now due to their long switching time and limited thermal stability. However, recent investigations show that suitable copolymers based on PVDF/TrFE copolymers in ultra-thin layers can achieve switching times of ≤100 ns. Nevertheless, the limited thermal stability of PVDF/TrFE copolymers prevent them from being integrated into the usual manufacturing process for Si-based data storage devices (D-RAM resp. S-RAM) and thereby frustrates the desired objective of producing nonvolatile random access memories (NV-RAMs). In the area of optical data storage technology, polycarbonate (PC) has established itself due to its favorable combination of properties. Thus, audio compact disks (CDs) are manufactured exclusively of PC, while high-flow PC types of high optical purity are clearly the preferred substrate material for optical data storage disks. The increasingly stringent requirements to be met in terms of lower birefringence and better thermal stability mean that the development of suitable modified or substituted polycarbonates is required. The development work being carried out worldwide in this area is reviewed here, and new suitable substituted polycarbonates with lower birefringence and significantly increased thermal stability up to glass temperatures of 238°C are presented. In addition, we deduce structure—property relationships for the above-mentioned structurally modified polycarbonates, specifically considering rotation potentials along the polymer backbone.     

螺噁嗪类光致变色化合物的合成研究进展

光致变色螺噁嗪;双光致变色螺噁嗪;螺噁嗪聚合物;合成;微波合成     

Alignment modulation of azobenzene-containing liquid crystal systems by photochemical reactions

Recent progress in alignment modulation of azobenzene-containing liquid crystal systems by photochemical reactions has been reviewed by dividing the modulation methods into two types: phase transitions (order–disorder change) and change of liquid crystal directors (order–order change). First, photochemical phase transitions and alignment changes of liquid crystals in guest/host mixtures and polymers are summarized. Then, alignment control of liquid crystals by linearly polarized light and photoactive surface layers is discussed. Finally, recent applications of alignment change and photochemical phase transitions of liquid crystals in holographic technology and photomechanical effects are introduced. In addition, future possible applications for a variety of practical devices, such as display devices, optical switching and reversible optical image storage, are mentioned.     

Recent developments in polymeric charge transfer complexes

The recent literature on polymeric charge transfer complexes is reviewed with emphasis on the author's own work. After a definition of the area and a survey of investigations on the spatial arrangement of donor and acceptor sites in the solid state, a variety of applications of these complexes is presented. Electrically conductive polymers are excluded. These applications are: compatibilization of polymer blends, liquid crystalline supramolecular organization, new developments in photo-conductivity, electroluminescence, nonlinear optical properties, photorefractivity and reversible optical storage.     

Photoresponsive liquid crystalline and amorphous polymers

Isomerization processes of azobenzene dyes dissolved in a glassy polymeric matrix or attached in glassy amorphous or liquid crystalline polymers to the backbone as side groups are induced by light. The isomerization process, in turn, causes the dye to reorient provided that polarized light is used: the long axis of the dye is oriented perpendicular to the polarization direction in the stationary case. Such a reorientation gives rise to strong modifications of the optical properties. This contribution is concerned with the analysis of the correlation between the nature of the azobenzene dyes, the isomerization, reorientation and modulations discussed above and with possible applications in the optical holographic storage. Considered are, in particular, dye/matrix combinations giving rise to nonlinear holographic responses, two photon holography, transient holographic modes applicable for holographic displays and the optical switching of other than optical properties.     

含偶氮苯光学活性侧基聚合物研究进展

综述了含偶氮苯光学活性侧基聚合物近年来的发展概况 ,介绍了多种聚合体系的类型。由于偶氮苯光于活性侧基的存在 ,使得这些聚合物具有光致变色性、非线性光学活性、光学各向异性等光学性能 ,在光信息存储材料、非线性光学材料、液晶材料、光电子器件、生物分子活性光调控、纳米技术等诸多领域都有广泛的应用。     

含偶氮基团的侧链液晶高分子的研究进展

综述了含偶氮基团的侧链液晶高分子的制备方法及其在可逆光信息存储与非线性光学领域的应用。     

Squaraine dyes: The hierarchical synthesis and its application in optical detection

Squaraine dyes, a four-membered ring system with structural rigidity, possess unique photoelectrical properties and are marked by their exceptionally sharp and intense absorption associated with a strong fluorescent emission in solution. These favorable characteristics have prompted their exploitation in a number of state of the art applications including photoconductivity, data storage, light-emitting field-effect transistors, solar cells and fluorescent histological probes. In this review, we first summarize the recently proposed novel methods in the synthesis of these versatile derivatives. Subsequently, their extensive applications in the prevalent optical detection of the surrounding medium such as ions, pH, thiol-based compounds, biomolecules and cell over the past decades are covered and discussed. In addition, different categories for the synthesis and sensing mechanisms for various squaric acid-based chemo-/bio- sensors are illustrated. Finally, the challenges and opportunities in the synthesis and application of these derivatives are also briefly discussed.     

Fluorescent microporous organic polymers: potential testbed for optical applications

Fluorescent microporous organic polymers (MOPs) are an emerging class of porous organic materials with considerable technological relevance due to great promise in a range of applications, in addition to typical usage in gas storage and catalysis. In this respect, innovative optical materials have been developed based on MOPs. In this Concept article, a brief appraisal of the fabrication methodologies of fluorescent MOPs in the form of bulk solid as well as in nanoparticles, their optical attributes, and promising application potentials are presented.     

Polarizability and optical rotation calculated from the approximate coupled cluster singles and doubles CC2 linear response theory using Cholesky decompositions

A new implementation of the approximate coupled cluster singles and doubles CC2 linear response model using Cholesky decomposition of the two-electron integrals is presented. Significantly reducing storage demands and computational effort without sacrificing accuracy compared to the conventional model, the algorithm is well suited for large-scale applications. Extensive basis set convergence studies are presented for the static and frequency-dependent electric dipole polarizability of benzene and C60, and for the optical rotation of CNOFH2 and (-)-trans-cyclooctene (TCO). The origin-dependence of the optical rotation is calculated and shown to persist for CC2 even at basis set convergence.     

INDIRECT VERSUS DIRECT TECHNIQUES FOR THE MEASUREMENT OF THE OPTICAL PROPERTIES OF TISSUES

Abstract Knowledge of the optical absorption and scattering properties of tissues is required to calculate the spatial distribution of light in vivo for applications such as photodynamic therapy. In many soft tissues in the visible wavelength range the optical albedo is high, the scattering is highly forward peaked, and the mean free path between photon interactions is small. This regime presents severe technical difficulties in measuring the absorption and scattering coefficients. Two classes of technique may be used: 1. indirect methods in which, by applying specific models of light propagation, the properties are deduced from measurements of bulk tissue properties, and 2. direct, model-free measurements using optically thin tissue samples. These two approaches are described and the relative advantages and disadvantages discussed. Data for the optical properties of model soft tissues at 630 nm are presented to illustrate the applications of indirect and direct methods.     

光致变色聚合物研究进展

本文主要介绍了9类光致变色聚合物的研究状况,包括光致变色螺吡喃聚合物、螺嗪聚合物、二芳基乙烯光致变色聚合物、偶氮苯类光致变色聚合物、苯氧基萘并萘醌光致变色聚合物、俘精酰亚胺光致变色共聚物、硫靛光致变色共聚物、双硫腙光致变色聚合物以及二氢吲嗪光致变色聚合物等。讨论了聚合物的合成、光致变色性质、影响聚合物性质的因素,并对光致变色聚合物未来的研究重点和方向作了展望。     

Energy Transfer in Dye‐Coupled Lanthanide‐Doped Nanoparticles: From Design to Application

Surface modification with organic dye molecules is a useful strategy to manipulate the optical properties of lanthanide‐doped nanoparticles (LnNPs). It enables energy transfer between dyes and LnNPs, which provides unprecedented possibilities to gain new optical phenomena from the dye–LnNPs composite systems. This has led to a wide range of emerging applications, such as biosensing, drug delivery, gene targeting, information storage, and photon energy conversion. Herein, the mechanism of energy transfer and the structural‐dependent energy‐transfer properties in dye‐coupled LnNPs are reviewed. The design strategies for achieving effective dye–LnNP functionalization are presented. Recent advances in these composite nanomaterials in biomedicine and energy conversion applications are highlighted.     

基于扫描探针显微镜(SPM)的高密度信息存储

随着信息技术的飞速发展,高密度信息存储的研究成为国际上备受关注的研究领域。扫描探针显微技术（SPM）通过改变材料的光、电、磁等局域特性可以实现纳米尺度的信息存储,成为提高信息存储密度的最有效手段之一。本文从信息存储材料和技术角度综述了基于SPM的高密度信息存储最近的研究进展,并讨论了其将来的研究和发展方向。     

Liquid crystal polymer optics

In this paper we give a concise overview of various optical applications of Liquid Crystalline side‐chain polymers. The possibility to tune the LC structure and phase‐diagrams, as well as the availability of methods to create specific structures in the director field, allows materials to be developed for data‐storage media and as optical compensation films for LC display applications.     

Current developments in optical data storage with organic dyes

The main motivation for the development of digital data storage has been the improvement in play‐back quality and the increase in storage capacity. In 1982 Philips and Sony introduced the first technically and economically successful system based on this—the compact disc (CD) and a compatible player. A very broad diversity of optical data recording formats are available today, and a difference is drawn between prerecorded, recordable, and rewritable media. This Review gives an overview of the systems used, the main features of production, and then concentrates on the properties of the organic dyes that are used in recordable systems. Dyestuffs chemistry has gained the reputation of having become a mature field of activity. Is this prejudice or a justified swan song for dyestuffs chemistry? When applications in optical data storage are considered, it is evident that even today progresses such as CD‐R and DVD/R would not be feasible without functional dyes.