Dendrimer families

Dendrons and dendrimers are the most intensely investigated subset of dendritic polymers. In the past decade over 2000 literature references have appeared on this unique class of structure controlled polymers. The term dendrimer was coined by Tomalia, et al. over 15 years ago in the first reports on poly(amidoamine) (PAMAM) dendrimers [75, 76]. It is derived from the Greek words dendri-(branch tree-like) and meros - part of). Poly(amidoamine) dendrimers constitute the first dendrimer family to be commercialized and undoubtedly represent the most extensively characterized and best understood series at this time. In view of the extensive literature information in this area, much of the remaining overview will focus on PAMAM dendrimers and will... 

Parallel studies on PAMAM dendrimers, the Frechet type polyether den-drons, and other dendrimer families have generated an extensive list of unique properties driven by the dendritic state/ Figure 1.18 compares several significant physical property differences between the linear and dendritic topologies related to conformations, crystallinity, solubilities, intrinsic viscosities, entanglement, diffusion/mobility and electronic conductivity. 

Unimolecular container/scaffolding behavior appears to be a periodic property that is specific to each dendrimer family or series. These properties will be determined by the size, shape, and multiplicity of the construction components that are used for the core, interior and surface of the dendrimer. Higher multiplicity components and those that contribute to tethered congestion will hasten the... 

Two different dendrimer families are presently commercially available Starburst polyamidoamine (PAMAM) dendrimers from Dendritech Inc., Midland, Michigan, and ASTRAMOL polypropyleneimine (PPI) dendrimers from DSM, Geleen, the Netherlands. 

To illustrate the most interesting electrochemical features of this family of dendrimers, it is reported the results obtained for three strictly related decanuclear compounds and the highest nuclearity compound of this dendrimer family, that is, a docosanuclear complex. 

The first reduction process occurring at 1.07 V versus Fc+/Fc is reversible the peripheral fullerene moieties behave independently from an electrochemical point of view in this dendrimer family. On the other hand, the first oxidation process is monoelectronic and it is centered on the Cu(I) complex the rate of heterogeneous electron transfer decreases upon increasing dendrimer generation. 

The Si-O-C sequence is the distinctive structural unit of carbosilanes. Like that of the carbosilanes, the scaffold of this dendrimer family can be constructed in a targeted manner by the choice of certain core units [88] (Table 4.4). Synthesis of carbosiloxanes generally proceeds by... 

The term dendritic effect [44] covers a multitude of diverse chemical and physical effects, whose common feature is that a change of certain properties or phenomena occurs with increasing or deceasing generation number within a dendrimer family. A dendritic effect is described as positive or negative, depending upon whether the observed effect is amplified or attenuated. 

Existing applications of dendrimers and dendritic polymers and those still in the planning stage are described together with the relevant properties. A number of characteristic general properties providing the basis for these applications are presented in a brief introductory overview. Other properties of specific dendrimer families are mentioned in Chapters 4 to 6. 

With the dendrimers series shown in Fig. 1, the order of AE° values was H2PO4- > HS04 > Cl" > NO3-. This order can, however, vary greatly from one dendrimer series to the other, and the same can be said of the dendritic effect some dendrimer families (such as the above one) give a strong dendritic effect for a given anion, and others do not. For instance, an amido-ferrocenyl dendrimer with an octabenzylated durene core and 24 redox termini underwent values of the order of what was found for the dendrimer 9-Fc of Fig. 1, far less than 18-Fc of Fig. 1. 

Just as ancestry and lineage can be traced in higher organisms, a molecular-level parallel is observed when these transformations are considered in the context of (1) stored molecular information at each dendrimer stage and (2) molecular information transferred (transcribed) to the progeny dendrimer surface at each transformation. For example, if the initiator core is thought of as a primitive abiotic gene [6-8] molecular details are sequentially transcribed and stored to produce interior and ultimately exterior (surface) features which are characteristic of that dendrimer family (phenotype). 

This approach has been used successfully to produce at least four different types of dendrimer families which include poly (arylester), poly (ary lene), poly(arylalkyl) ether, and poly(aryl/azacrown ether) type dendrimers. 

A repertoire of possible defects that might be encountered in the synthesis of many of these dendrimer families is as illustrated in Fig. 31. 

Clearly, this proposed congestion at the critical branched state M, should exhibit (1) sterically-inhibited reaction rates, (2) sterically-induced stoichiometry, and, quite possibly, (3) a critical phase change due to surface cooperativity (association). These phenomena have been observed experimentally for the Starburst PAMAM dendrimers and may prove to be diagnostic probes for this critical branched state in other dendrimer families. 

Fullerenes and carbon nanotubes are formed spontaneously based on the restricted rules of carbon linkage. Therefore, their fundamental frameworks are not easily redesigned. Superstructures where we are free to design their sizes and shapes are sometimes more attractive prospects. In this section, the dendrimer family is introduced, as examples of artificially controllable superstructures. The word dendrimer contains the root dendr- , which means tree, an accurate reflection of the structures of dendrimers - molecular trees. The first dendrimer was proposed by Tomalia. After several groups had... 

The following conclusion from all examples of families reported above can be expressed although some dendrimer families have been reported to present nonlinear enhancements in terms of TPA response, in particular dendrimers based on triphenylamines, most branched molecules were shown to exhibit no perturbation, i.e. only additive effect, in their TPA efficiency with respect to that of the corresponding Unear system it is worth noting that several other dendritic systems have been shown to confirm this trend [152], As for Unear molecules, Kuzyk presents the limits of this den-drimeric approach [105,106]. 

MAJOR APPLICATIONS Used as templates for initiation of caprolactam polymerization to produce injection moldable star-like-Nylon-6 products. This dendrimer family has been used in a variety of metal chelation, coatings, and lubrication-typo applictions. ... 

Dendrimers have attracted considerable attention in the polymer field over the past two decades as they have been recognized as the most important macromolecules possessing tunable internal packing density, void volumes, solvent-dependent size, branching dimensions, and surface functionalities. Since the first report of a dendrimer-like molecule in 1978 [33], significant progress has been made in the dendrimer chemistry. A large number of dendrimer compositions (families) and dendrimer surface modifications have been reported. A plethora of applications related to controlled release of pharmaceuticals have been reported. Currently, there are two widely studied dendrimer families, namely the Tomalia-type polyamidoamine (PAMAM) dendrimers and the Frdchet-type polyether dendrimers. PAMAM dendrimers are the first complete dendrimer family to have been synthesized. 

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