Supramolecular nonlinear optical materials

The supramolecular structure of block co-polymers allows the design of useful materials properties such as polarity leading to potential applications as second-order nonlinear optical materials, as well as piezo-, pyro-, and ferroelectricity. It is possible to prepare polar superlattices by mixing (blending) a 1 1 ratio of a polystyrene)-6-poly(butadiene)-6-poly-(tert-butyl methacrylate) triblock copolymer (SBT) and a poly (styrene)-Apoly (tert-butyl methacrylate) diblock copolymer (st). The result is a polar, lamellar material with a domain spacing of about 60 nm, Figure 14.10. 

Wenbin, L. Weiping, L. Wong, K.W. Marks, T.J. Supramolecular approaches to second-order nonlinear optical materials. Self-assembly and microstructural characterization of intrinsically acentric [(Aminophenyl)azo)]-pyridinium superlattices. J. Am. Chem. Soc. 1996. 118 (34), 8034. 

Dramatic advances in molecular synthetic chemistry have led to a high level of control over molecular interactions. However, we are only at the beginning of a more extended design of chemical interactions in two and three dimensions. If we learn how to control the structure, properties, and stability of desired supramolecular assemblies, many areas in materials science and technology, such as microelectronics, optics, sensors, and catalysis, will benefit substantially. Representative areas of research activity include selective monolayer assemblies on electrode surfaces functionalized pillared layered materials and assemblies of conductors, semiconductor clusters, or nonlinear optical materials in three-dimensionally ordered hosts such as zeolites. 

The study of chiral materials with nonlinear optical properties might lead to new insights to design completely new materials for applications in the field of nonlinear optics and photonics. For example, we showed that chiral supramolecular organization can significantly enhance the second-order nonlinear optical response of materials and that magnetic contributions to the nonlinearity can further optimize the second-order nonlinearity. Again, a clear relationship between molecular structure, chirality, and nonlinearity is needed to fully exploit the properties of chiral materials in nonlinear optics. 

The chemistry of metal complexes featuring alkyne and alkynyl (acetylide) ligands has been an area of immense interest for decades. Even the simplest examples of these, the mononuclear metal acetylide complexes L MC=CR, are now so numerous and the extent of their reaction chemistry is so diverse as to defy efforts at a comprehensive review. " The utility of these complexes is well documented. Some metal alkynyl complexes have been used as intermediates in preparative organic chemistry and together with derived polymeric materials, many have useful physical properties including liquid crystallinity and nonlinear optical behaviour. The structural properties of the M—C=C moiety have been used in the construction of remarkable supramolecular architectures based upon squares, boxes, and other geometries. ... 

Nonlinear optical (NLO) properties are usually considered to depend on the intrinsic features of the molecule and on the arrangement of a material. An intermediate level of complexity should also be taken into account, that of the formation of well-defined supermolecules, resulting from the association of two or more complementary components held together by a specific array of intermolecular interactions (1). Such intermolecular bonding may yield more or less pronounced NLO effects in a variety of supramolecular species (2). Thus, three levels of nonlinear optical properties may be distinguished the molecule, the supermolecule and the material. The molecular and supramolecular levels involve respectively - intramolecular effects and structures, -... 

Nagamura describes in Chapter 9 the fabrication and properties of supramolecular and polymeric systems that display unique linear and nonlinear optical response. Such materials may find application in high-density information processing systems of the future. Chapter 10, by Shinkai and James, describes the properties of supramolecular photoswitchable ion receptors. Finally, in Chapter 11, Ishikawa and Ye discuss the application of state-of-the art fluorescence methods to explore the properties of polymers with nm-scale resolution. 

Supramolecular structures obtained via self-assembly processes may be named as another future topic, which just starts an increasingly rapid development.294 By some examples it was already demonstrated how molecular chirality may by translated into supramolecular chirality in such self-assembled structures and this may lead not only to new, improved host-guest systems but also eventually to new materials in a more general sense. Liquid-crystalline systems or materials for nonlinear optics may be mentioned just as two examples. 

A continuous research work on membrane properties and fundamental aspects of transport phenomena in the various membrane operations is important for the fumre of membrane science and technology. There is a need for both basic and applied research to develop new membranes with improved properties and new membrane processes. These research efforts must take into account the studies done in other areas such as supramolecular chemistry, molecular imprints materials, nanotechnology, nonlinear optics, studies on biological membranes and biological phenomena, etc. 

Hoss. R. Konig, O. Kramer-Hoss. V. Berger. U. Rogin. P. Hulliger. J. Crystallization of supramolecular materials Perhydrotriphenylene (PHTP) inclusion compounds with nonlinear optical properties. Angew. Chem. Int. Ed. Engl. 1996. 35. 1664-1666. 

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