History of Dendrimer Characterization

The earliest work on dendrimer characterization was concerned with aspects of the organic chemistry - did the proposed chemical reaction take place without side reactions and what was the conversion Since near-100% conversion and near-perfect removal of excess reactants is required for making pure dendrimer, common methods of spectroscopy and chromatography can be used to verify the structure. In a wide variety of dendrimer chemistries, nearly perfect structures have been produced, at least for earlier generations wherein the techniques are more quantitative. 

The development of mass spectroscopic techniques such as matrix assisted laser desorption (MALDI) and electrospray mass spectrometry has allowed the absolute determination of dendrimer perfection [7,8], For divergent dendrimers such as PAMAM and PPI, single flaws in the chemical structure can be measured as a function of generation to genealogically define an unreacted site of or a side reaction producing a loop at a particular generation level. Mass spectromet-ric results on dendrimers, not only demonstrate the extreme sensitivity of the technique, but also demonstrate the uniformity of the molecular mass. The polydispersity index of Mw/Mn for a G6 PAMAM dendrimer can be 1.0006 which is substantially narrower than that of living polymers of the same molecular mass [7], 

Transmission electron microscopy (TEM) [1, 18-20] has been used to image individual dendritic molecules, usually the larger generations. More recently, atomic force microscopy (AFM) [21] has also been used to image dendritic molecules. 

---