Polymers dendrimer

Entries on new materials, including re-cyclate plastics, fullerenes, hard-surfaced polymers, dendrimers, transflective materials, rapid prototyping materials, silicone nitride, supercritical fluids, bulk molding compounds, conversion coatings, folic acid, replacements for chloro-fluorocarbons ... 

Unlike linear or ordinary branched polymers, dendrimers display intrinsically low viscosity, even at high mass. As standard polymeric molecules increase in mass and size, their viscosity normally increases continually. With dendrimers, viscosity increases only up to about the fourth generation, after which it actually begins to decline (Mourey, 1992 Frechet, 1994). In addition, with control over the type of pendent groups that adorn the surface, dendrimers can maintain high solubility regardless of size. 

As described below, ionic catalyst complexes can be supported to both inorganic and polymer (dendrimer) carriers. The efficiency of the support is determined by the general rules of ion exchange and, for this reason, in order to achieve a successful approach it is important to exclude the formation or presence of other ionic compounds, which might compete for (liberate) the catalyst ion from the support. 

In contrast to traditional polymers, dendrimers are unique core-shell structures possessing three basic architectural components namely, (I) a core, (II) an interior of shells (,generation) consisting of repetitive branch cell units and (III) terminal functional groups (i.e. the outer shell or periphery) as illustrated in Figures 1.13 and 1.14. 

Several groups have engaged in the study of linear polymer-dendrimer conjugates (i.e. architectural copolymers). These structures combine block copolymer and dendrimer branching features within one molecular architecture [69-71],... 

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. 

Ferrocene-based Branched Polymers (Dendrimers). One of the topics in macromolecular chemistry is constituted by dendrimers, or hyperbranched macromolecules of tridimensional globular structure, the surface of which is characterized by a large number of functional groups, Scheme 4. Such functionalities impart to the molecules solubility, viscosity and thermal properties different from those of the common linear polymers.38c,d 44... 

Choi, J.S., Lee, E.J., Choi, Y.H., Jeong, Y.J. and Park, J.S. (1999) Poly(ethylene glycol)-block-poly(L-lysine) dendrimer novel linear polymer/dendrimer block copolymer forming a spherical water-soluble polyionic complex with DNA. Bioconjug. Chem., 10, 62-65. 

SCS-MP2 and the new perturbative B2-PLYP density functional methods provide accurate reaction barriers and outperform MP2 and B3-LYP methods when applied to the 1,3-dipolar cycloaddition reactions of ethylene and acetylene.39 Phosphepine has been shown to catalyse the asymmetric 3 + 2-cycloaddition of allenes with a variety of enones (e.g. chalcones) to produce highly functionalized cyclopentenes with good enantiomeric excess.40 The AuPPh3SbF6 complex catalysed the intramolecular 3 + 2- cycloaddition of unactivated arenyne- (or enyne)-yne functionalities under ambient conditions.41 A review of the use of Rh(I)-catalysed 3 + 2-cycloadditions of diaryl-and arylalkyl-cyclopropenones and aryl-, heteroaryl-, and dialkyl-substituted alkynes to synthesise cyclopentadienones for use in the synthesis of natural products, polymers, dendrimers, and antigen-presenting scaffolds has been presented.42... 

Compared to polymers, dendrimer architectures offer favourable conditions for fixation of catalytically active moieties thanks to their monodispersity, variability, structural regularity of the molecular scaffold, and numerous functionalisation possibilities. Catalytic units can be fixed - multiply if required - on the periphery, in the core of a dendrimer, or at the focal point of a dendron. If the dendrimers are suitably functionalised at the periphery, appropriate metal complexes can be directly attached to the surface of the molecule. In contrast, dendrimers functionalised in the core or at the focal point shield the catalytically active site through their shell structure in a targeted manner, for example to attain substrate selectivity in the case of reactants of different sizes [1]. The corresponding concepts of exodendral and endodendral fixation of catalysts were inttoduced in the context of functionalistion of carbosilane, polyether, and polyester dendrimers [2]. Exodendral fixation refers to attachment of the catalytic units to the... 

Keywords Dithiafulvene -Conjugated polymer Dendrimer Polyrotaxane Thioketene dimer... 

Because of the commercial interest in amphiphilic block copolymers the properties of the amphiphilic linear polymer-dendrimer have been most extensively studied. An illustration of the various phases that can be observed is shown in Fig. 6 for the case of an ABA type block copolymer, where A is the hydrophobic dendrimer and B the hydrophilic PEO [119]. The exact location of the... 

Starburst polymers (dendrimers ) [A. Morikawa, M. Kakimoto, Y. Imai, Nippon Gomu Kyokaishi 1992, 65(4), 205-212],... 

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