Block polymers, dendritic

To address the zinc dendrite problem in nickel-zinc cells, eVionyx claims to have developed a proprietary membrane system that is nonporous, has very high ionic conductivity, is of low cost, and can block zinc dendrite penetration even in high concentrations of KOH. The polymeric membrane has an ionic species contained in a solution phase thereof. The ionic species behaves like a liquid electrolyte, while at the same time the polymer-based solid gel membrane provides a smooth impenetrable surface that allows the exchange of ions for both discharging and charging of the cell. 

For polymer chemists it is interesting to know how well-known linear polymers can be linked with dendritic architectures and what the supramolecular consequences of this approach might be. Combination of dendrimers with linear polymers in hybrid linear-dendritic block copolymers has been employed to achieve particular self-assembly effects. Block copolymers with a linear polyethylene oxide block and dendritic polybenzylether block form large micellar structures in solution that depend on the size (i.e., the generation) of the dendritic block [10]. Amphiphilic block copolymers have been prepared by the combination of a linear, apolar polystyrene chain with a polar, hydrophilic poly(propylene imine) dendrimer [11] as well as PEO with Boc-substituted poly-a, -L-lysine dendrimers, respectively [12]. Such block copolymers form large spherical and cylindrical micelles in solution and have been described as superamphi-philes and hydra-amphiphiles , respectively. 

Keywords polysiloxanes, cyclotrisiloxanes, anionic polymerization siloxane copolymers, block copolymers, dendritic polymers... 

Polyether-b-polyester dendrimer 3,5-dihydroxybenzyl alcohol as monomer for ether-linked fragments and 2,2,2-trichloroethyl 3,5-dihydroxybenzoate for ester linked fragments radially alternating the dendritic segments produced segmented-block polymer and concentric alternation gave layer-block polymer spectroscopy, thermal characterization described. [269]... 

Comprehensive reviews of nomenclatiu-e for structure-based and source-based representations for dendritic, hyperbranched, and hyper-cross-linked polymers (21,35-38), and for star and star-block polymers (21), have been published. 

Over a period of about 50 years, representation of polymer structures, both on paper and in databases, has developed from a virtually random system to a highly organized and sophisticated one. Polyoners are represented sometimes by structure-based methods, sometimes by source-based methods, and sometimes by both. Both methods survive because each offers advantages and disadvantages. Both methods involve structural representation of polymers by a precisely defined set of rules developed over several decades by CAS, lUPAC, and the Committee on Nomenclature of the Division of Polymer Chemistry of the ACS. Areas still in need of improved representation are copolymers of imterminated SRU types aftertreated (post-treated) polymers, and dendritic (52), hyperbranched, hyper-cross-linked, star, and star-block polymers. Also needed are hierarchical relationships between intellectually related polymers (53). 

A polymer, by conventional definition, is a macromolecule made up of multiple equivalents of one or more monomers linked together by covalent bonds (e.g., carbon-carbon, amide, ester, or ether bonds) [1]. These conventional polymers come in many configurations for example, linear homopolymers, linear copolymers, block copolymers, cross-linked polymers, dendritic polymers. 

Gitsov, I. (2000) Hybrid dendritic capsules properties and binding capabilities of amphiphilic copolymers with dendritic architecture. In J.E. Glass (ed.), Associative Polymers in Aqueous Media, ACS Symposium Series 765. American Chemical Society, Washington, DC, pp. 72-92. Kurjata, J., Chojnowski, J., Yeoh, C.T., Rossi, N.A.A. and Holder, S.J. (2004) Synthesis of poly[dimethylsiloxane-block-oligo(ethylene glycol) methyl ether methacrylate] an amphiphilic copolymer with comb-like block. Polymer, 45,6111-6121. 

Hirao, A., Hayashi, M., Loykulnant, S. et al. (2005b) Precise syntheses of chain-multi-functionaUzed polymers, star-branched polymers, star-hnear block polymers, densely branched polymers, and dendritic branched polymers based on iterative approach using functionalized 1,1-diphenylethylene derivatives. Progress in Polymer Science, 30,111-182. 

Dendritic, Hyperbranched, Hypercrosslinked, Star, and Star-block Polymers... 

A star polymer may also comprise an unknown number of arms connected to the center of the cluster by addition to the reaction mass of a second, multifunctional monomer or SRU that ties all the linear growing polymer chains together into a crosslinked (microgel) core. These are sometimes called star-branch polymers. Cloutet et al., however, describe a star-branched polymer as a dendritic block polymer . A third type of star polymer comprises a dendritic core from which emanate a known number of arms. In any of these types of star polymers, the arms may be all the same, or different arms may have different compositions the latter are known variously as hetero-star, miktoarm star, or variegated star polymers. ... 

Puskas, J.E. Dendritic (arborescent) pol3tisobutylene-polystyrene block copolymers DMTA analysis and swelling studies, Polym. Mater. Sci. Eng., 91, 875-876, 2004. 

Puskas, J.E. BiocompatibiUty studies of novel dendritic polyisobutylene-based block copolymers, Polym. Prepr., 45, 412- 13, 2004. 

Polymers and copolymers are among the most beneficial materials produced by synthetic chemistry. The invention and commercialization of new polymeric materials with radical new properties provides an opportunity to monopolize the market and justify the expense involved in the research and development. The commercialization of new polymers or copolymers always presents scale-up and design challenges. Scientists have recently developed new polymeric materials whose commercial impact has yet to be realized. Examples are semiconductive and conductive polymers and amphiphilic dendritic block copolymers. Other promising materials, such as polymers for (targeted) drug delivery and... 

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