FTIR spectroscopy studies of dendrimers built from cyclophosphazene core

Abstract

The FTIR spectra of seven generations of phosphorus dendrimers built from cyclotriphosphazene core with terminal phenoxy groups and theirs all-D isotope species have been recorded and analyzed. Their spectral pattern is determined by the ratio T/ R ( T, the number of terminal groups, R, the number of repeating units). This ratio trends to r − 1 ( r, branching functionality of repeating unit), and becomes constant, when the generation number is higher than 3–5. Experimental IR spectra of generations higher than four are very close similar, according theoretical approach. The dependence of band full width at half height in the IR spectra on generation number is established. The influence of the encirclement on the band frequencies and intensity was studied and due to the predictable, controlled and reproducible structure of dendrimers the information usually inaccessible was obtained. Bands assigned to the core, repeated units and terminal groups of dendrimers were separated by the differential spectroscopy method. From the differential IR spectra of dendrimers it follows that for the generations higher than four, the steric congestion disturbs the conformations of the terminal groups. The rather rigid repeated units with little conformational flexibility define the perfect microstructure of phosphorus-containing dendrimers up to six generation. FTIR spectroscopy provides the unique detailed information about the structure of technologically relevant materials, which could not be obtained before with any other technique.