Dendrites, concepts

Such mesogenic systems represent a class by themselves often referred to as dendromesogens. The dendritic concept results from the self-organization of these dendromesogens into various liquid crystalline morphologies. Cylindrical supramolecular dendrimers are generally obtained by the self-assembly... 

In a second novel approach, Mullen and co-workers further developed an inter-molecular repetitive Diels-Aldcr procedure for the generation of dendritic and hy-perbranched poly(phenylcnc)s. Hereby, they applied the concept of reacting A2B-type monomers, in this case monomers containing both cyclopcnladienone (dien-... 

This modular concept allows for the synthesis of monodisperse dendritic phen-ylene dendrimers of the first (43a, 22 benzene rings) and second (43b, 62 benzene rings) generation [65]. Due to the dense packing of the phenylene rings, shape-persistent nanostructures result. Several of these large phcnylene-type dendrimers (e.g. 43a) can be further cyclized to giant polycyclic PAHs. 

In this decade, all chemistry research fields have adopted and/or applied the dendrimers and/or dendrimer methodologies. The table of contents of this series. Topics in Current Chemistry Dendrimers Volumes I-IV, clearly indicates this situation [1-4], that is, the concept of dendritic compounds has already been introduced in host-guest and/or supramolecular chemistry (Vol. I/Chap. 2, Vol. Il/Chaps. 3,4, Vol. IV/Chap. 3), chiral chemistry (Vol. I/Chap. 4), electrochemistry (Vol. I/Chap. 6, Vol. Ill/Chap. 3), heteroatom and/or organometalHc chemistries (Vol. I/Chap. 3, Vol. Il/Chaps. 2,5, and Vol. IV/Chap. 4), and carbohydrate chemistry (Vol. IV/Chap. 6), as well as applied in the field of medicine (Vol. Il/Chap. 6) and nanoscience (Vol. Ill/Chap. 4). The dendrimer methodology is expected to be used in future novel science as a conventional chemistry concept. 

What research objectives should dendrimer chemistry therefore target as the second stage of this science The answer is the progress of macromolecular chemistry while maintaining the dendrimer concept, even if we do not use molecules with the dendritic shape. 

The maturity of dendrimer chemistry has led to confusion among researchers, because there are no specific research objectives in this field. It may be a good idea to design and synthesize a novel macromolecule, a non-dendrite-shaped molecule, keeping the concept of the dendrimer in mind. The nano-sized closed space inside the molecule is one of the key concepts for novel macromolecular chemistry. 

Newkome GR, Moorefield CN, Vogtle F (1996) Dendritic molecules concepts, synthesis, perspectives. VCH, Weinheim... 

This manuscript describes the dendritic macromolecules for optical and optoelectronic apph-cations, particularly stimulated emission, laser emission, and nonlinear optics. Dendrimers have been designed and synthesized for these applications based on simple concepts. A coreshell structure, through the encapsulation of active imits by dendritic branches, or a cone-shaped structure, through the step-by-step reactions of active imits, can provide particular benefits for the optical high-gain media and nonlinear optical materials. It also described experimental results that support the methods presented for designing and fabricating functionalized dendrimers for optoelectronic applications, and theoretical results that reveal the intermolecular electronic effect of the dendritic structure. 

The early VN neurones migrate by various routes and in mammals become organised into two layers, each with distinct functional attributes (Chaps. 2 and 6). Amongst marsupials, the sensory cells of an opossum appear at about one-week post-conception (Jia and Halpem, 1998). Despite their extremely altricial developmental pattern, the bandicoots dendrites produce sensory processes (Fig. 4.5) on the lumenal border of the VNO at 35 days postnatal, which in the Northern Bandicoot (Isoodon macrourus) is about 50% of pouch life (Kratzing, 1986). 

The Concept of Migration-Dependent Dendritic Cell Activation... 

Other types of branched peptide dendrimers, known as multiple antigen peptides (MAPs), have been synthesized to mimic proteins for applications, for instance as synthetic vaccines, serodiagnostics, peptide inhibitors and intracellular delivery vehicles. Since this concept has been recently described in detail elsewhere [11], only the conceptual framework will be briefly presented here. Tam and coworkers have developed a dendritic core based on lysine units for the construction of MAPs [12-15] (Fig. 3). Carrying antigens at their periphery these MAPs have been designed to increase antigenicity and immunogenicity of peptides. 

Recently, Tam et al. extended their orthogonal ligation concept, using the thermodynamically driven formation of a thiazolidine ring for the synthesis of dendritic compounds that carry cyclic peptides at the surface, which were designated multiple cyclic antigen peptides (McAPs) [18,19]. 

Concept The structural motif of a defined branching of branches leads to dendritic molecules reaching the nanometer scale. The development of this concept has given rise to a great variety of macromolecules which... 

By the development of these concepts leading to the efficient synthesis of dendritic architectures,151 a new impetus has been given in organic and inorganic chemistry which is leading to the production of new materials. Possible applications will be dis-... 

Since they were first mentioned in 1978, the concept of cascade or dendritic structures has witnessed a meteoric rise. On the one hand, thanks to their aesthetic beauty, and on the other hand, because of their broad applicability, dendrimers are in considerable demand. As the concept is not limited to one class of substances and, furthermore, allows a simple access on several routes, there is -besides the researchers who started dendrimer chemistry - a growing number of research groups which are dendritically expanding their special areas of interest in different ways and describing new or varying already existing properties. 

For comprehensive review of the synthesis of different dendrimers, see G. R. Newkome, C. N. Moorefield, F. Vogtle, Dendritic Molecules Concepts, Synthesis, Perspectives , WILEY-VCH, Weinheim 1996. 

It is appropriate to compare the well-known concepts of covalent bond formation in traditional organic chemistry with those that apply to classical polymer chemistry and to dendritic macromolecular chemistry. This allows one to fully appreciate the differences between the three areas in the context of structure control, in concert with issues related to terminal group and mass amplification. 

Flory was the first to hypothesize concepts [28,52], which are now recognized to apply to statistical, or random hyperbranched polymers. However, the first purposeful experimental confirmation of dendritic topologies did not produce random hyperbranched polymers but rather the more precise, structure controlled, dendrimer architecture. This work was initiated nearly a decade before the first examples of random hyperbranched4 polymers were confirmed independently in publications by Odian/Tomalia [53] and Webster/Kim [54, 55] in 1988. At that time, Webster/Kim coined the popular term hyperbranched polymers that has been widely used to describe this type of dendritic macromolecules. 

The concept of making brush-type polymers in which a linear polymer is funtionalized with dendritic side-chains was first suggested by Tomalia in a 1987 patent, though actual experimental work on his approach was only reported recently recently [15]. Hawker and Frechet were first to document the preparation of a vinyl copolymer containing a few pendant Frechet-type dendrons (Figure 7.9). 

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