Hyperbranched dendritic

This volume of Topics in Current Chemistry aims to highlight major developments in the field and it shows the efforts of chemists from various subdisciplines of chemistry to design new dendritic molecules focusing on novel properties, functions, and potential applications. Hyperbranched/dendritic molecules containing silicon, phosphorus, and other elements are reported apart from hydrocarbon, carbohydrate and nucleic acid cascade molecules. 

In contrast, polydispersity is a characteristic property of hyperbranched dendritic polymers, and results from the formation of by-products as a result of cycli-... 

Fig. 2.15 Synthesis of a hyperbranched dendritic polymer (from a FCn monomer schematic). F=functional group, C=coupling site...

While not so structurally perfect (see Sections 1.3 and 1.4) as their dendritic relatives, these hyperbranched dendritic compounds (see Section 2.7) can be produced faster and at less expense, making them especially interesting for the materials sector. The various commercially available monomers (Fig. 4.51) offer great structural versatility. 

The solid-phase preparation of hyperbranched dendritic polyamides, based on 3,5-di-aminobenzoic acid, was attempted but deemed to have severe limitations , such as the critical condensation reaction could not be forced to completion. The accessibility of chain ends within the solid support was suggested1381 to be the major obstacle to high yield conversion. 

Ye and co-workers exploited the shear stability of highly branched, high molecular weight polyethylenes (PEs) as lubricant viscosity index improvers [252, 253]. Viscosity index of a lubricant is a critical parameter which defines its quality and application temperature range. They synthesized PEs with controllable chain topologies ranging from linear to a hyperbranched dendritic structure by chain walking polymerization [254]. The PE samples were blended into a base paraffinic oil (density 0.8659 g mL at 15 °C, kinematic viscosity 30.06 cST at 40 °C) to form lubricants. The lubricants were subjected to the Kurt Orbahn (KO) test to measure the shear stability index, which is expressed by... 

Cationic hyperbranched dendritic poly amidoamine [PAMaM) chitosan... 

B. Pettersson and K. Sorensen, High-solids aikyds based on hyperbranched (dendritic) polymers A new concept with new opportunities , in Proceedings of... 

M. Suzuki and co-workers reported the preparation of hyperbranched dendritic polyamines by multibranching polymerizations of cychc carbamates (Scheme 68). 

Figure 7 Two principal synthetic methods for building up hyperbranched dendritic macromolecules (a) divergent and (b) convergent methods.

Similarly, Wang and coworkers [271] reported that hyperbranched dendritic structures possessing poly(3-alkylthiophene) arms self-assemble into thin films with morphological features, as well as electrical and optical properties that reveal a surprising degree of structural order. Typical conductivities varied between 42 and 65 sec/cm. 

As a unique method of controlled/living radical polymerization, ATRP has had a tremendous impact on the synthesis of macromolecules with well-defined compositions, architectures, and functionalities, including star- and comb-like polymers as well as branched, hyperbranched, dendritic, network, cyclic type structures and so forth. 

Hawker CJ, Lee R, Frechet JMJ (1991) One-step synthesis of hyperbranched dendritic... 

On the other hand, amphiphilic graft [78, 79] copolymers also present interesting phase behavior in solution. In the aspect of preparation of star-like or graft polymers, hyperbranched/dendritic chains are usually acted as a multi-sites... 

Fujiki, K Sakamoto, M. Satoh. T. Tsubokawa, N. (2000). Postgrafting of Hyperbranched Dendritic Polymer from Terminal Amino Groups of Polymer Chains Grafted onto Silica Surface. Journal of Macromolecular Science, Pure and Applied Chemistry, A37, 357-377... 

Similarly, Wang and coworkers [193] reported that hyperbranched dendritic structures possessing poly(3-alkylthiophene) arms self-assemble into thin... 

Star and hyperbranched (dendritic) polymers have attracted increasing attention in organic, supermolecular, and polymer chemistry as well as coordination chemistry because of their specific structures and characteristics [1-5]. For the preparation of these highly branched polymers, two kinds of synthetic methods have been developed a one-step pol)nnerization and a stepwise method. By the one-step method, various star and hyperbranched polymers with many structural and functional group variations have been prepared [6-10]. On the other hand, the stepwise method is quite useful, especially for the synthesis of dendritic polymers. Both divergent and convergent s)mthetic approaches have been employed [2,11]. 

III. SYNTHESIS OF HYPERBRANCHED DENDRITIC POLYAMINE BY Pd-CATALYZED RING-OPENING POLYMERIZATION OF CYCLIC CARBAMATE... 

In order to prepare a hyperbranched dendritic polymer by chain polymerization, a new concept of pol)mierization, termed multibranching polymerization (MBP) was proposed, which provides a dendritic polymer involving the initiator as the core [23] The most characteristic aspect of MBP is multiplication of the propagating ends at every step of propagation according to Scheme 5 ... 

Dendritic macromolecules are hyperbranched fractal-like structures that emanate from a central core and contain a large number of terminal groups. Two synthetic approaches have been reported for the preparation of these macromolecules the divergent [76-78] and convergent growth approaches [79-82]. In both methods many synthetic steps are necessary to produce high molecular weight materials. To avoid synthetic problems, the macromonomer with hyperbranched dendritic moiety may be one of the most useftil materials for the dendritic macromolecules. 

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