THE SYNTHESIS AND CHARACTERIZATION OF A NEW FAMILY OF POLYAMIDE DENDRIMERS

A new family of dendrimers has been constructed with 5-hydroxyisophtha lic acid and diethanolamine as the sources of the branching units. The design of a second-generation building block in the form of an orthog onally-protected aminotetraacid (a single diethylphosphoramide-protect ed amine and four methyl-ester-protected carboxylic acid groups) has b een established by a series of logical developments involving the synt hesis of various dendrimer prototypes. This building block has been ut ilized in both convergent and divergent methods in the synthesis of mo nodisperse dendrimers up to the fourth generation and subsequently pol ydisperse sixth-generation dendrimers at the level of a mixture. One-, two-, and three-directional dendrimers of the second and fourth gener ation were synthesized in order to carry out detailed comparisons by G PC and by H-1 NMR spectroscopy. The GPC results suggest that the fourt h-generation dendrimers adopt globular shapes, while the variable-temp erature NMR spectroscopic investigations demonstrate that the peripher y of the fourth-generation dendrimer is less mobile than either of its internal regions or the analogous portions of the second-generation d endrimer. Molecular modeling suggests highly globular shapes for the l arger dendrimers and gives values for molecular radii in very close ag reement with those obtained from analysis of the GPC results.