Dendrimers internal structure

We have presented a new method of using SANS to elucidate the radial structure of dissolved dendrimers [23, 24]. It has been demonstrated that SANS in conjunction with contrast variation [32-37] is a valid tool to determine the internal structure of dendrimers. The main result of [23,24] is the clear proof that the density distribution has its maximum at the center of the molecule. Hence this corroborates the general deductions of theory as discussed in the preceding section. 

Variation of contrast [46] is an important experimental technique in neutron small-angle scattering. Above and beyond size determination, it affords detailed insights into the internal structure of dissolved dendrimers and even permits the location of selected components of the molecule which have been previously labelled with deuterium. 

M.R Ottaviani, R. Valluzzi, L. Balogh, Internal Structure of SUver-Poly(amidoam-ine) Dendrimer Complexes and Nanocomposites, Macromolecules 35, 5105, 2002. D.S. Deutsch, G. Lafaye, D. Liu, B.D. Chandler, C.T. Williams, M.D. Amiridis, Decomposition and Activation of Pt-Dendrimer Nanocomposites on a Silica Support, Catalysis Letters 97, 139, 2004. 

Newkome and coworkers have modified their diaminoanthraquinone-containing dendrimers [56] by incorporating a redox-active aromatic nitro-containing group into the internal structure of the dendrimer. These compounds were studied by cyclic voltammetry, and it was determined that the presence of the nitro group had a significant effect on the redox process of the AQ moiety, causing the peak potential of the AQ reduction to shift 100 mV in the positive direction [72]. 

M. F. Ottaviani, R. Valluzzi and L. Balogh, Internal structure of silver-poly(amidoamine) dendrimer complexes and nanocomposites. Macromolecules, 35(13), 5105-5115 (2008). 

This chapter presents a selective glimpse of this dynamic family of spherical macromolecnles for newcomers to the topic in order to help them better appreciate the field that has been extensively reviewed elsewhere. This chapter is divided into several parts to emphasize the structmal diversity and their potential applications. First, a study of the internal structure of the dendritic architecture, emphasizing the different types, followed by a study of their interactions with other molecules or atoms, such as in the case of host-guest chemistry, molecular recognition, or encapsulation inside the dendrimer. Finally, there is a small section that will address the intermolecular interactions of dendrimers and dendrons to either themselves or other nano-objects. In this past quarter century, tens of thousands of papers have been published producing a wide variety of different dendritic architectures with varied structural components capable of novel supramolecular interactions. Therefore, only an overview describing their structure with representative examples and practical purposes will be discussed, when appropriate. 

As shown in this chapter, ESR provides a very useful technique for the study of dendrimer properties and their local environments, not only when paramagnetic species are directly involved in the dendrimer original structure, but also when paramagnetic units are added as spin probes or spin labels to the dendrimers. The advantage of the ESR technique with respect to other spectroscopic methods of analysis mainly resides in the ability to select the proper spin probe or spin label able to monitor, like a special camera, a selected area internally or externally to the dendrimer. Of course, the basic request is to know if and how the probes or the labels modily the dendrimer properties. 

Khopade AJ, Khopade SA, Tripathi PK, Jain NK. 2007. Spongesomes Vesicles from poly(amidoamine) dendrimer doped phospholipids with a sponge-like internal structure. (Unpublished manuscript). 

Caminade AM, Majoral JP (2005) Phosphorus dendrimers possessing metallic groups in their internal structure (core or branches) syntheses and properties. Coord Chem Rev 249 1917-1926... 

At this stage two strategies (one of them outlined in Scheme 37) can be developed to start the construction of dendrimers within the cascade structure of 88-[G3]. Each of them allows the synthesis of six internal dendrimers of generation 4 into the internal voids of 88- [G3]. 31P NMR constitutes an extraordinary and unique tool for monitoring the construction of these controlled polydendritic structures (see Fig. 9 for illustration). Chemical shifts of phosphorus groups are different from one generation to another and the intensities of signals are of... 

The facile functionalization of the cavities allow the development of a macro-molecular chemistry within the cascade structure of dendrimers. As an example six dendrimers of generation 4 were built into the internal voids of a dendrimer of generation 3. 

Regardless of how they are made, the higher the dendrimer generation the greater the density of its branching becomes. Dendrimers of small size have an internally open configuration that freely permits the flow of small molecules within their inner structure. As dendrimers increase in diameter from G-0 through G-7, their appearance and size becomes more and more similar to... 

In general, dendrimers of size G-0 through G-3 have open, asymmetric, and flexible structures with effectively no protected internal areas, due to a large freedom of motion in their branches, and they can readily accommodate additional covalent attachments to their surfaces. See Figures 73-7.5 for illustrations of the two-dimension and three-dimension structure of a... 

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