Supramolecular self-assembled films

Molecular calculations provide approaches to supramolecular structure and to the dynamics of self-assembly by extending atomic-molecular physics. Alternatively, the tools of finite element analysis can be used to approach the simulation of self-assembled film properties. The voxel4 size in finite element analysis needs be small compared to significant variation in structure-property relationships for self-assembled structures, this implies use of voxels of nanometer dimensions. However, the continuum constitutive relationships utilized for macroscopic-system calculations will be difficult to extend at this scale because nanostructure properties are expected to differ from microstructural properties. In addition, in structures with a high density of boundaries (such as thin multilayer films), poorly understood boundary conditions may contribute to inaccuracies. 

Self-assembly, in supramolecular chemistry, 24 49—50 Self-assembly thin film preparation method, 17 57-58... 

Salditt, T. Schubert, U. S. Layer-by-layer self-assembly of supramolecular and biomolecular films. Rev. Molec. Biotech. 90, 55-70 (2002). 

Salditt, T. Schubert, U.S. Layer-by-layer self-assembly of supramolecular and biomolecular films. Rev. Mol. Biotechnol. 2002, 90 (1), 55-70. Ball, P. Made to Measure New Materials for the 21st Century, Princeton University Press, 1998. Tirrell, M. Kokkoli, E. Biesalski, M. The role of surface science in bioengineered materials. Surf. Sci. 2002, 500 (1-3), 61-83. 

Interfacial structure The role of electrochemical phenomena at interfaces between ionic, electronic, photonic, and dielectric materials is reviewed. Also reviewed are opportunities for research concerning microstructure of solid surfaces, the influence of the electric field on electrochemical processes, surface films including corrosion passivity, electrocatalysis and adsorption, the evolution of surface shape, and self-assembly in supramolecular domains. 

A second class of monolayers based on van der Waal s interactions within the monolayer and chemisorption (in contrast with physisorption in the case of LB films) on a soHd substrate are self-assembled monolayers (SAMs). SAMs are well-ordered layers, one molecule thick, that form spontaneously by the reaction of molecules, typically substituted-alkyl chains, with the surface of soHd materials (193—195). A wide variety of SAM-based supramolecular stmctures have been generated and used as functional components of materials systems in a wide range of technological appHcations ranging from nanoHthography (196,197) to chemical sensing (198—201). 

The main supramolecular self-assembled species involved in analytical chemistry are micelles (direct and reversed), microemulsions (oil/water and water/oil), liposomes, and vesicles, Langmuir-Blodgett films composed of diphilic surfactant molecules or ions. They can form in aqueous, nonaqueous liquid media and on the surface. The other species involved in supramolecular analytical chemistry are molecules-receptors such as calixarenes, cyclodextrins, cyclophanes, cyclopeptides, crown ethers etc. Furthermore, new supramolecular host-guest systems arise due to analytical reaction or process. 

In this chapter we describe the basic principles involved in the controlled production and modification of two-dimensional protein crystals. These are synthesized in nature as the outermost cell surface layer (S-layer) of prokaryotic organisms and have been successfully applied as basic building blocks in a biomolecular construction kit. Most importantly, the constituent subunits of the S-layer lattices have the capability to recrystallize into iso-porous closed monolayers in suspension, at liquid-surface interfaces, on lipid films, on liposomes, and on solid supports (e.g., silicon wafers, metals, and polymers). The self-assembled monomolecular lattices have been utilized for the immobilization of functional biomolecules in an ordered fashion and for their controlled confinement in defined areas of nanometer dimension. Thus, S-layers fulfill key requirements for the development of new supramolecular materials and enable the design of a broad spectrum of nanoscale devices, as required in molecular nanotechnology, nanobiotechnology, and biomimetics [1-3]. 

Molecular organization and self-assembly into layers, membranes, vesicles etc., construction of multilayer films [7.1-7.5], generation of defined aggregate morphologies [4.74, 4.75, 7.6-7.8J etc., make it possible to build up specific supramolecular architectures. The polymerization of the molecular components has been a major step in increasing control over the structural properties of such assemblies [7.9-7.13]. 

Crystallization amounts by nature to the self-assembly of very large, boundaryless supramolecular species. Its control is a goal of major importance in order to be able to generate solid-state materials of specific structural and physical properties (see also Sections 7.1, 7.2, 9.4.4 [7.39-7.42, 9.105, 9.245]). Supramolecular effects play a crucial role. Directional growth of materials may be induced by a template and involve molecular recognition [9.246], occurring by epitaxy [9.247] or on oriented thin films [9.248]. 

Figure 14.11 Two-step self-assembly process of rod-coil oligomer via mushroom shaped nanostructures into polar supramolecular films. The TEM image represents a top view of such a supramolecular film (Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced by permission).

Electrostatic self-assembly was combined with supramolecular chemistry to obtain inclusion complexes of a polymeric nonlinear optical (NLO) active dye and modified [3-cyclodextrin with induced chromophore orientation [37], The polyanion is a N,N-diallyl-aniline and sodium-2-acrylamido-2-methylpropanesulfonate copolymer functionalized with pendant azo group. The modified /i-cyclodextrin oligo-cation was obtained by treatment of hcptakis(6-dco y-6-iodo-/i-cyclodcxtrin) with excess pyridine. A linear polyamine, chitosan, was also combined with the polyanion, for comparison. Films were deposited on glass slides by dipping them alternatively in aqueous solutions of the cation and the polyanion. UV-visible spectra indicate dye aggregation and suggest the formation of an inclusion complex of the dye with the cyclodextrin, thus isolating the chromophores. 

The stepwise construction of self-assembled organic/inorganic multilayers based on multivalent supramolecular interactions between guest-functionalized dendrimers and nanoparticles and host-modified gold nanoparticles has been developed, yielding supramolecular LbL assembly (Fig. 13.8).12 Multilayer thin films composed of... 

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