Elementoorganic dendrimer characterization by Raman spectroscopy

Abstract

The FT-Raman (10–3500 cm −1) spectra of ten generations of the elementoorganic dendrimers have been recorded and analyzed for the first time. Their spectral pattern is determined by the ratio N t/ N r ( N t—number of terminal groups, N r—number of repeating units). This ratio trends to m r−1 ( m r—branching functionality of repeating unit), and becomes constant, when the generation number is higher than 3–5. Experimental Raman spectra of generations higher than 4 are very close similar, according theoretical approach. The dependence of line full width at half height in Raman spectra on generation number is established. The low frequency Raman spectra in R( ν) representation are used to investigate the librations of terminal groups. The possibility appears to separate the lines assigned to the core, repeated units and terminal groups of dendrimers by difference spectroscopy method. From the difference Raman spectra of dendrimers it follows that for the generations higher than six steric congestion disturb the conformations of terminal groups. FT-Raman spectroscopy provides unique detailed information about the structure of the technologically relevant materials, which could not be obtained before with any other technique.