Dendrimers internal environment

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. 

The intensity of the ESR signal provides a measure of the radical concentration and is evaluated by double integration of the ESR signal, based on an intensity reference. Variation of the ESR intensity indicated the entrance-exit of a paramagnetic probe from the dendritic box, or the oxidation-reduction of a paramagnetic label or ion belonging to the dendrimer. Variation of relative intensify of a spectral component provided a measure of the distribution of paramagnetic species in different locations and environments at the external and/or internal surface of the dendrimers. 

Dendrimers are nanometer-sized, highly branched and monodisperse macromolecules with symmetrical architecture. They consist of a central core, branching units and terminal functional groups. The core together with the internal units, determine the environment of the nanocavities and consequently their soiuhiiizing properties, whereas the external groups the solubility and chemical behaviour of these poiymers [53]. 

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