Dendritic structures cavity size

Initial efforts gave rise to well-characterized dendritic macromolecules, but applications remained limited because of the lack of specific functionalities. An exponential increase of publication volume observed for about 15 years testified the growing interest for dendrimers and has led to versatile and powerful iterative methodologies for systematically and expeditiously accessing complex dendritic structures. The perfect control of tridimensional parameters (size, shape, geometry) and the covalent introduction of functionalities in the core, the branches, or the high number extremities, or by physical encapsulation in the microenvironment created by cavities confer such desired properties as solubility, and hydrophilic/hydrophobic balance. Thus, creativity has allowed these structures to become integrated with nearly all contemporary scientific disciplines. 

Dendrimer interior functional groups and cavities can retain guest molecules selectively, depending on the nature of the guest and the dendritic endoreceptors, the cavity size, the structure, and the chemical composition of the peripheric groups. Two main methods are known for the synthesis of metal nanoparticles inside dendrimers. The first method consists of the direct reduction of dendrimer-encapsulated metal ions (Scheme 9.4) the second method corresponds to the displacement of less-noble metal clusters with more noble elements [54]. 

The cavities and voids inside dendritic structures are of great importance, particularly in the study of supramolecular systems. The nature of this void, how it is affected by dendrimer size, constitution and solvent are of supreme importance in relation to potential applications [15], It is therefore necessary to discover ways to characterize the microenvironment in the dendrimer. Many investigators have made use of functional probes in order to study dendritic microenvironments [56,57], These probes are either attached covalently to the dendrimer or introduced as guest species and the effects of solvent and dendrimer size on the microenvironment are then studied. 

A special case is the formation of the balls of the size from about 200 pm containing deep cavities with the fem-like dendrites formed on the bottom of cavities and more or less dense cauliflower structure on the surface of these balls. Fig. 2.27d. The cross section of such agglomerate is shown in Fig. 2.28b. For some reasons this agglomerate started to grow as a ball, again starting from disperse (in the middle) and finishing with compact deposit at the surface for a reason... 

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