Applications of Dendrimers

Dendrimers are versatile chemicals, and their surfaces, interiors and cores can be engineered to provide a range of properties that give them potential 

One example has used a manganese porphyrin and iodobenzene encapsulated within a dendrimer to bring about shape-selective epox-idation of alkenes. The important aspect of catalysts is that the reactants can move rapidly to the active site, and that the products can be removed rapidly from the active site and expelled from the dendrimer. 

It is possible to take advantage of the differing characteristics of the periphery and the interior to promote chemical reactions. For example, a dendrimer having a non-polar aliphatic periphery with highly polar inner branches can be used to catalyse unimolecular elimination reactions in tertiary alkyl halides in a non-polar aliphatic solvent. This works because the alkyl halide has some polarity, so become relatively concentrated within the polar branches of the dendrimer. This polar medium favours the formation of polar transition states and intermediates, and allows some free alkene to be formed. This, being nonpolar, is expelled from the polar region, and moves out of the dendrimer and into the non-polar solvent. This is a highly efficient process, and the elimination reaction can be driven to completion with only 0.01 % by mass of a dendrimer in the reaction mixture in the presence of an auxiliary base such as potassium carbonate. 

FIGURE 5.6 Schematic representation of dendritic copolymers with different polarities (a) segment-block dendrimer and (b) layer-block dendrimer. (From Klajnert, B. and Bryszewska, M., Acta Biochimica Polonica, 48, 199, 2001. With permission.) 

In a certain copolymer system, the reactivity ratios are = 0.001 and rj = 0.002. Sketch the copolymer composition diagram expected for this pair of monomers. 

Mayo et al. (1948) have reported reactivity ratios for the copolymerization of vinyl acetate (reactivity ratio = with eight representative monomers (corresponding reactivity ratio = fj). 

Determine the composition of the copolymer obtained when an equimolar 

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Structure, physical properties, and applications of dendrimers including heterocyclic fragments 99CRV1665. 

We have found that dendrimers can be used to encapsulate active moieties, thereby preventing them from interacting. This passivation effect limits inter-molecular interactions such as self-aggregation and molecular clustering. We also found that dendrimers can be made dipolar. This asymmetry in molecular orientation enables dendrimers to be used in NLO. In this chapter we describe our application of dendrimers to lasers and NLO. 

One of the main applications of dendrimers is in catalysis allowing easy recycling of the homogeneous catalyst by means of nanofiltration. Carbosilane dendrimers functionalized with diphenylphosphine groups at the periphery have been synthesized and characterized. Palladium complexes of these dendrimers have been used as catalysts in the allylic alkylation reaction. These dendrimeric catalysts can be used in a continuous process using a membrane reactor.509... 

M. J. Cloninger, Biological applications of dendrimers, Curr. Opin. Chem. Biol., 6 (2002) 742-748. 

Many of the applications of dendrimers involve the covalent coupling of other molecules to the dendrimer surface or to points within the branched structure. These attached molecules... 

Since the pioneering work on dendritic structures by Vogtle et al.,[28] dendrimers have attracted much attention. The synthesis and investigation of their structural properties became a new field in science. The application of dendrimers as support molecules for homogeneous catalysts was first reported by Van Koten et al. in 1994.[29] Dendrimers have the advantage of having perfect structures unlike polymeric structures and are... 

Dendrimers with terminal functional groups represent mode compact precursors that are spherical and almost monodisperse, with reactive groups placed on their periphery. Their synthesis, structure and properties have been reviewed in monographs and review articles often together with hyperbranched polymers (cf., e.g. [15-20]), as well as in this book. Application of dendrimers as precursors for conventional materials is limited at this time by their relatively high cost. 

The classic application of dendrimers terminated with functional groups as precursors of polymer networks to obtain products such as coatings, composites, or RIM materials, with advanced technological and materials properties are relatively scarce. The higher cost of dendrimers is undoubtedly one of the main reasons. 

Interest in dendritic polymers (dendrimers) has grown steadily over the past decade due to use of these molecules in numerous industrial and biomedical applications. One particular class of dendrimers, Starburst polyamidoamine (PAMAM) polymers, a new class of nanoscopic, spherical polymers that appears safe and nonimmunogenic for potential use in a variety of therapeutic applications for human diseases. This chapter will focus on investigations into PAMAM dendrimers for in vitro and in vivo nonviral gene delivery as these studies have progressed from initial discoveries to recent animal trials. In addition, we will review other applications of dendrimers where the polymers are surface modified. This allows the opportunity to target-deliver therapeutics or act as competitive inhibitors of viral or toxin attachment to cells. 

Dendrimers are well-defined hyperbranched macromolecules, and the larger ones have characteristic globular structures. Dendrimer chemistry has become extremely popular since the preceding decades, and several potential applications of dendrimers, including catalysis (/), are well documented in several reviews (2). Recent... 

II. Catalyst Recycling in Applications of Dendrimer-Supported Catalysts... 

The many possibilities of directing the physical/chemical properties of a den-drimer by introduction of selected functional groups into the molecule lead to an great variety of potential applications of dendrimers. Depending upon the position and the nature of the functional units within the dendrimer structure, it is possible to distinguish between different types of functional dendrimers ... 

Possible applications of dendrimers with chiral branching scaffold... 

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. 

The examples of applications of dendrimers are admittedly often only of a potential character, yet nevertheless reflect the broad range of possibilities covering practically all areas from materials of construction to medicine [86 b[. Precisely the latter area paces strict demands on applications with respect to purity and compatibility with the human organism. 

The syntheses and applications of dendrimers and hyperbranched polymers have attracted considerable scientific interest in recent years. These highly branched polymers possess... 

Research on dendrimers was first focused on synthetic aspects concerning this new class of macromolecules, and a broad range of dendrimers is now available, some even commercially. The emphasis of current study has shifted from merely synthetic aspects to questions of practical applications of dendrimers and the ways in which these unique compounds are superior to known systems. Consequently, much more useful synthetic procedures are required. Schliiter et al. have reported the synthesis of dendrimers with poly(p-phenylene) (PPP) derived cores using the Suzuki polycondensation [139]. 

The size and shape of dendrimers have been estimated using transmission electron microscopy [14]. Producing better images of dendrimers may supply answers to fundamental questions such as whether dendrimers have truly uniform sizes, spherical shapes, and dense cores. The visualization of dendrimer assemblies would also be helpful to confirm the structure and morphology for many applications of dendrimers. The positively stained PAMAM dendrimers are shown in Fig. 2 for G10 to G5, respectively. The dendrimer molecules appear as dark objects on a light background of the amorphous carbon substrate and they are well separated from each other. The shapes of the stained molecules are spherical to a first approximation for G10 to G7, with some molecules showing... 

Scott RW1, Wilson OM, Crooks RM (2005) Synthesis, characterization, and applications of dendrimer-encapsulated nanoparticles. 1 Phys Chem B 109 692-704... 

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