Hyperbranched structure stars

There are several methods to deliberately introduce branching to polymers prepared by ATRP. This includes various graft-and comb-shaped copolymers, branched and hyperbranched structures, stars, and networks. 

The self-condensing copper-catalyzed polymerization of macromonomer of poly(tBA) with a reactive C—Br bond (H-6) affords hyperbranched or highly branched poly(tBA).447 Copolymerization of H-1 and TV-cyclohexylmaleimide induced alternating and self-condensing vinyl polymerization.448 The residual C—Cl bond was further employed for the copper-catalyzed radical homopolymerization of styrene to give star polymers with hyperbranched structures. Hyperbranched polymers of H-1 further serve as a complex multifunctionalized macroinitiator for the copper-catalyzed polymerization of a functional monomer with polar chromophores to yield possible second-order nonlinear optical materials.325... 

Another approach to incorporate a block structure was to use the multifunctional precursor shown in Fig. 35 and grow blocks from the core of the hyperbranched structure. Such star-like polymers with 80 pnBA blocks were obtained [ 130]. In a similar way, hyperbranched polymers from VBC were used to initiate the ATRP of nBA [130] and St [264]. Dendrigraft polystyrene was found to display a lower intrinsic viscosity and higher thermal stability than linear polystyrenes [264]. 

Triptycene (151) is a simple example of a star topology for a bigraph. Harold Hart has built on this motif in his design of heptaiptycene (152) tritriptycene (153) and supertriptycene [230]. These rigid hyperbranched structures are among the first dendritic structures and show remarkable inclusion properties. Depicting these structures as their graph reductions evokes additional mole-... 

In this subsection we will consider (distinct from the dendrimers of Sect. 8) another class of regular hyperbranched polymers. We recall that the quest for simpUcity in the study of complex systems has led to fruitful ideas. In polymers such an idea is seating, as forcefully pointed out by de Gennes [4j. Now, the price to be paid in going from linear chains to star polymers [33,194[, dendrimers [13,33,194,205] and general hyperbranched structures [216[ is that scaling (at least in its classical form) is not expected to hold anymore (at least not in a simple form, which implies power-law dependences on the frequency CO or on the time f). One of the reasons for this is that while several material classes (such as the Rouse chains) are fractal, more general structures do not necessarily behave as fractals. 

Although these materials may find applications that are predicted for hyperbranched polymers, they are used rather as precursors allowing (either by using hydroxyl groups directly or after their transformation into required initiating groups) the synthesis of multiarm star polymers of different structures. Star polymers containing poly(EOx) core may... 

Space limitations preclude more than an overview of these types aftertreated (post-treated), alternating, block, comb and graft, crosslinked, dendritic, hyperbranched, hypercrosslinked, star, and star-block. Comprehensive reviews of structure-based and source-based representations for them have been published. ... 

B. Self-Ordering of Star Polymer and Macromonomer Having Hyperbranched Structure... 

Fig. 28. The ratio A2M [rj] at large for star molecules (symbols) and randomly branched structures [25,26,108,130,131]. The shaded area indicates the range of the experimental findings with randomly and hyperbranched samples [144]. The line was drawn to guide the eye...

Many micellar catalytic applications using low molecular weight amphiphiles have already been discussed in reviews and books and will not be the subject of this chapter [1]. We will rather focus on the use of different polymeric amphiphiles, that form micelles or micellar analogous structures and will summarize recent advances and new trends of using such systems for the catalytic synthesis of low molecular weight compounds and polymers, particularly in aqueous solution. The polymeric amphiphiles discussed herein are block copolymers, star-like polymers with a hyperbranched core, and polysoaps (Fig. 6.3). 

Fig. 6.3 Different types of micelles and micelle analogous structures a) amphiphilic block copolymers, b) star-like polymers with a hyperbranched core, c) polysoaps.

Macrotnolecules are formed by covalent bonding of a large number of monomeric units. This results in a wide variety of possible structural architectures, e.g. linear chains, branched chains, brush-like chains ( hairy rods ), star-like, tree-like ( hyperbranched ), perfectly branched ( dendritic ) structures (Figure 1) [14,15],... 

To synthesise polymers with unusual properties from existing basic monomers one needs to place the monomer units in ordered arrays rather than at random. Thus polymer architecture control remains an important area of research. Possible structural elements include block, graft and comb copolymers as well as star and dendritic/hyperbranched topographies. Potential for such structures in the surface coatings and adjacent industries include use as... 

Anionic polymerization has proven to be a very powerful tool for the synthesis of well-defined macromolecules with complex architectures. Although, until now, only a relatively limited number of such structures with two or thee different components (star block, miktoarm star, graft, a,to-branched, cyclic, hyperbranched, etc. (co)polymers) have been synthesized, the potential of anionic polymerization is unlimited. Fantasy, nature, and other disciplines (i.e., polymer physics, materials science, molecular biology) will direct polymer chemists to novel structures, which will help polymer science to achieve its ultimate goal to design and synthesize polymeric materials with predetermined properties. 

Most functional polymers are based on simple linear backbones. These can be chain-end (telechelic), in-chain, block or graft structures. However, there has also been interest in functional polymers with special topologies or architectures. These include 3-dimensional polymers, such as stars, hyperbranched polymers, or dendrimers " (treelike structures) (Scheme 1)... 

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