Amine-terminated dendrimers

Combinatorial approach to unsymmetrically tiered macromolecules [214] is a brand new area of research which would allow dendrimerization of materials (e. g., glass, classical polymers, fibers) and thus enable fine tuning of macromole-cular properties. For example, treatment of an amine terminated dendrimer with a mixture of complementary, isocyanate-based monomers [215, 216] affords a heterogeneous surfaced dendrimer. Selective transformation of the surface nitrile moieties via metal-catalyzed reduction to obtain a new polyamine dendrimer allows further combinatorial-based elaboration as illustrated in Fig. 42. 

Knecht, M.R. and Wright, D.W. (2004) Amine-terminated dendrimers as biomimetic templates for silica nanospheres formation. Langmuir, 20, 4728-4732. 

Apart from DAB-dendr-(CN)4, which is a white crystalline solid, all generations are colorless to slightly yellow oils. The amine-terminated dendrimers are transparent, whereas the nitrile-terminated products are somewhat turbid. The solubility of the dendrimers is determined primarily by the nature of the end-group DAB-dendr-(NH2)n is soluble in H20, methanol and toluene, whereas DAB-dendr-(CN)n is soluble in a variety of common organic solvents. 

All dendrimers consist of inner tertiary amines, located at the branching points of the various dendritic shells (layers). The amine-terminated dendrimers, furthermore, have basic primary amine end-groups. Basicity is therefore one of the most dramatic properties of the polypropylene imine) dendrimers, and has been studied via titration experiments and calculations. Titration experiments of the dendrimers have been performed in water using 1 M hydrochloric acid. Only two equivalence points are observed for DAB-J nJr-(NH2)4 in a ratio of 2 1. From these titrations, pKa values of 10.0 (primary amine groups) and 6.7 (tertiary... 

The general chemistry used in this approach involves the combination of a limited amount of an amine-terminated dendrimer core reagent with an excess of carboxylic acid terminated dendrimer shell reagent [31]. These two charge differentiated species are allowed to self-assemble into the electrostatically driven supramolecular core-shell tecto(dendrimer) architecture. After equilibration, covalent bond formation at these charge neutralized dendrimer contact sites is induced with carbodiimide reagents (Scheme 1). 

Scheme 7.9. Use of a disulfide linker for the non-site specific connection of amphipathic peptides and carbohydrates to amine terminated dendrimers.

Scheme 9.2. Representations of potential randomly constructed networks via the reaction of ester terminated dendrimer and amine terminated dendrimer.

Connection of dendrimers via treatment with multifunctional cross-linking-type reagents such as the addition of polyhalides to amine-terminated dendrimers 78 results in randomly positioned dendritic assemblies. Dendrimers have also been bridged by the incorporation of copolymerizable units into reactions with dendrimers possessing polymerizable, terminal olefins. 79,80 ... 

Reaction of various primary amine-terminated dendrimers with either inorganic or organic acids allows the preparation of a wide variety of crystalline derivatives. One such intermediate was implicated in the development of lyotropic phases [156] when octanoic acid was combined with Starburst poly(ethylenimine) (generation-3). 

All dendrimers consist of inner tertiary amines, located at the branching points of the different dendritic layers. The amine-terminated dendrimers furthermore have... 

Dendrimers can be reacted with a variety of compounds to further functionalize them to give them unique characteristics. For example, amine-terminated dendrimer can be reacted with imsaturated nitriles to give a polynitrile dendrimer. In another case the polyamine dendrimer can be reacted with jS-unsat-urated amides to give amide-terminated dendrimer. A whole host of possibilities can be visualized based on the reactivity of the amino group [43]. 

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