Stars and Dendrimers

Finally, a dendrimer containing 243 ferrocenyl units at the periphery was synthesized by ferrocenylsilation of an allyl terminated dendrimer. This macromolecule could be oxidized to the corresponding stable ferrocenium dendrimer and reversibly reduced back to the neutral complex. Cuadrado and coworkers have also been active in the synthesis of dendrimers containing ferrocene and cobaltocene moi- 

The synthesis of propylenimine based dendrimers with up to five generations and 64 peripheral ferrocenyl moieties underwent reversible oxidation at 1/2=0.59 Polymer 213 is an example of a dendrimer with 32 ferrocenyl units at the periphery. 

The guest-host relationships of some low-generation dendrimers with cyclodextrins were examined. While dendrimers with 4 and 8 peripheral 

Deschenaux et al. have investigated the synthesis of ferrocenyl-based polymers (217) with liquid crystalline properties 

While ferrocene-derived polymers continue to be the best studied of the metallocene-based polymers, there exists a wide variety of other (symmetric) metallocenes. The metallocene portion of the polymer can be bound through the metallocene ring, through adjacent metallocene rings, or through the metal itself. Metallocenes may exist 

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Then we address the dynamics of diblock copolymer melts. There we discuss the single chain dynamics, the collective dynamics as well as the dynamics of the interfaces in microphase separated systems. The next degree of complication is reached when we discuss the dynamic of gels (Chap. 6.3) and that of polymer aggregates like micelles or polymers with complex architecture such as stars and dendrimers. Chapter 6.5 addresses the first measurements on a rubbery electrolyte. Some new results on polymer solutions are discussed in Chap. 6.6 with particular emphasis on theta solvents and hydrodynamic screening. Chapter 6.7 finally addresses experiments that have been performed on biological macromolecules. 

Polymeric micelles, stars and dendrimers in solution consist of a number of polymer chains that form relatively compact aggregates that exhibit internal dynamics and overall diffusion. Whereas the association of polymer in a micelle is usually driven by physical interactions, the star and dendrimer architecture is generally achieved by chemical bonds. 

Gold nanoparticle-alkanethiolate-ferrocenyl Stars and Dendrimers... 

Gold nanopartide-alkanethiolate-ferrocenyl Stars and Dendrimers are Excellent Oxo-Anion Sensors that can Provide Derivatized Electrodes... 

Although other deprotonated complexes are sometimes not as stable as [CpFe( 5-QMesCF )], they can be generated and used at low temperature to form the desired bonds [27e]. Using the base and electrophile in excess, the reactions can be carried out at room temperature because the deprotonated species immediately reacts with the electrophile in situ. This kind of deprotonation/alkylation sequence underpins the star and dendrimer construction described herein (vide infra). In this way, the complexes [FeCp( s-arene)][PF6] also act as proton reservoirs [33]. 

Angot, S., et al. (2000), Amphiphilic stars and dendrimer-like architectures based on poly(ethylene oxide) and polystyrene, Macromolecules, 33, 5418-5426. 

Chain architecture linear, grafts, blocks, stars and dendrimers. 

A variety of metal acetylide-containing stars and dendrimers have been synthesized.329-332 Dendrimer 280 was prepared via reaction of a chloro-substituted platinum complex 278 with ethynyl functionalized dendron 279 in the presence of Cul (Scheme 2.73).329 This method generated dendrimers with up to 45 platinum units. 

Star and dendrimer core molecules were prepared by the peralkylation or allylation of cyclopentadienyliron complexes containing methyl-substituted arenes.298,301,302,304-311,333 The preparation of water-soluble metallodendrimers containing six cationic cyclopentadienyliron moieties, 281, has also been reported.301 Dendrimer 281 was tested for potential use as a redox catalyst for the cationic reduction of nitrates and nitrites to ammonia. 

In the robust, very easily accessible cationic complexes [FeCp(arene)][PF6]10 (Cp = h5-cyclopen-tadienyl), the benzyhc protons are more acidic than in the free arene because of the electron-withdrawing character of the 12-electron CpFe+ moiety. For instance, FeCp(C6Me6) Pl6 is more acidic by 15 pKa units (pKa = 28 in DMSO) (DMSO = dimethyl sulfoxide) than in the corresponding free arene (pKa = 43 in DMSO). Asa result, these complexes are much more easily deprotonated than the free arene.11 This key proton-reservoir property led us to synthesize stars and dendrimers in an easy way.12 Indeed, reaction of [FeCp(C6Me6)][PF6], with excess KOH (or i-BuOK) in THF (THF = tetrahydrofuran) or DME (DME = 1,2-dimethoxyethane) and excess methyl iodide, alkyl iodide, allyl bromide, or benzylbromide results in the one-pot hexasubstitution (Scheme 11. la).5,13,14 With allyl bromide (or iodide) in DME, the hexaallylated... 

Polymers made from the same compounds can have different properties depending on how they are made. These differences in physical properties result from differences in the overall structure of the polymer chain. The three major structural types— linear, branched, and cross-linked—are illustrated in Figure 27.5. Other, more specialized, structural types— ladders, stars, and dendrimers— have unique properties and are under active investigation. 

Essential Features and Properties of Stars and Dendrimer-Like Polymers... 

Gnanou, Y., and Taton, D. (2001). Stars and dendrimer-like architectures by the divergent method using controlled radical polymerization. Macromol. Symp., /74(Polymerization Processes and Pol5mer Materials I) 333-341. 

D. Mery, C. Ornelas, J. Ruiz, S. Cordier, C. Perrin, D. Astrac - MogBrg-Cluster-Cored Organometallic Stars and Dendrimers, in Inorganic Clusters, C. Perrin Ed., C.R. Chimie 8, 1789,200S. 

There are two kinds of fix point solutions of the RR that describe the bulk behavior [15]. In the 1-cycle solution, the fix point solution becomes independent of the index m as we move toward the origin m = 0 on an infinite cactus, and is represented by x. For the current problem, it is given by x = 1 /2, as can be checked explicitly by the above RR in (10.48). It is obvious that it exists at all temperatures. There is no singularity in this fix point solution at any temperature. This solution corresponds to the disordered paramagnetic phase at high temperatures and the SMS below the melting transition to be discussed below. The other fix point solution is a 2-cycle solution, which has been found and discussed earlier in the semiflexible polymer problem [36, 37, 44, 46-48], the dimer model ]37], and the star and dendrimer solutions [48]. The fix point solution alternates between two values xj and x on two successive levels. At T = 0, this solution is given either by xj = 1 and x = 0, or by Xj = 0 and xj = 1. The system picks one of these as the solution. At and near T = 0, this solution corresponds to the low-temperature AF ordered phase, which represents the CR and its excitation at equal occupation, and can be obtained numerically. The... 

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