Polyamide and polyamine dendrimers: Synthesis, characterization and application as unimolecular micelles and homogeneous catalysts

Scope and limitations. The principal objectives of this project were to synthesize new classes of amphiphilic dendrimers, to characterize their structures, and to study their applications as unimolecular micelles and homogeneous catalysts in aqueous solution. The syntheses of three classes of dendrimers were planned using convergent strategies and surface modification. The characterization of the functionalized dendrimers was planned using NMR and MS analysis. The dendritic microenvironments and the unimolecular micellar capabilities of the target dendrimers were to be probed using NMR and UV spectroscopy, molecular modeling and kinetic studies.; Findings and conclusions. Amphiphilic dendrimers with alternating arms and alternating generations and dendrimers having ester and amide chain ends were synthesized using convergent synthesis or surface modification. The structures of those dendrimers were characterized by FT-IR, 1H and 13C NMR, LSI-MS, MALDI-TOF and ESI-MS analysis. The dendrimers having alternating arms can change their conformations with respect to the change in solvent polarity as demonstrated by 1H NMR analysis and 13C spin-lattice relaxation time (T1) measurements. The hydrodynamic sizes of the amphiphilic dendrimers were determined by dynamic light scattering (DLS) measurement and also estimated by molecular simulation. The amphiphilic dendrimers can change their conformations with respect to the change in solvent polarity as demonstrated by 13C spin-lattice relaxation time (T1) measurements. The unimolecular micellar capabilities of the dendrimers having alternating arms and alternating generations were examined by UV spectroscopy using pyrene as environment polarity indicator. The rates of the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate ion in aqueous solution catalyzed by the amphiphilic dendrimers having polyammonium sites in the interior are up to 500 times faster than the rate of the control experiment.