Weak nanostructured materials

As has already been mentioned in the discussion of the stacking model, such equations are particularly useful for the analysis of nanostructured material with weak disorder in order both to assess the perfection of the material and to discriminate among lattice and stacking models (cf. Sect. 8.8.3). 

What role do weak interactions play in self-assembly of molecular and nanostructured materials ... 

It is remarkable that this - more or less - first publication on this topic already contained the main questions and ideas that are still in the focus of many investigations supramolecular structure of the ionic liquid phase, ion-pairing and the interaction of ILs with solute (or solvent) molecules. The same group continued their investigations and subsequently focussed on a larger variety of imidazolium salts with different weakly-coordinating anions (BF 4, PF 6, and BPh 4) [7]. They were able to demonstrate that each cation was surrounded by at least three anions (and vice versa) and by this fashion hydrogen-bound supermolecules were present in the liquid state. Therefore, one could honestly speak of ILs as nanostructured materials . 

Nanocarbon structures such as fullerenes, carbon nanotubes and graphene, are characterized by their weak interphase interaction with host matrices (polymer, ceramic, metals) when fabricating composites [99,100]. In addition to their characteristic high surface area and high chemical inertness, this fact turns these carbon nanostructures into materials that are very difficult to disperse in a given matrix. However, uniform dispersion and improved nanotube/matrix interactions are necessary to increase the mechanical, physical and chemical properties as well as biocompatibility of the composites [101,102]. 

In more recent years there is a development towards molecular recognition as a tool. Based on the increasing understanding of the weak forces between (macro) molecules we now see new concepts of material design. Chapters 1 to 3 cover three aspects of this development nanostructures that are formed by self-assembly of small molecules (chapter 1), dendritic structures (chapter 2) and polymers (chapter 3). A volume of a series like Perspectives in Supramolecular Chemistry can never claim to cover all aspects of a subject. All I can hope is that these chapters are representative of the filed of supramolecular technology. 

It is useful in discussion of weak coupling between nanostructures to remember the nonradiative mechanism of Forster resonant energy transfer from an excited molecule (a donor) to some other molecule (an acceptor) which can be in the ground or in an excited state. The probability of such a transfer is determined by the Coulomb nonretarded (instantaneous) dipole-dipole interaction between molecules and is proportional to Rp/R6 where Rp is the Forster radius and R is the distance between molecules. For organic materials the Forster radius is usually about several nanometers and strongly depends on the overlapping... 

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