Comb-branched copolymer

Fig. 7.13 Structure of comb-branch copolymers used as SPEs...

Comb-branched copolymer and block copolymer architectures are similar in that they are generally based on short polyether chains supported in some manner to give the material its mechanical stability. Success has been variable in attempts to... 

To obtain improved ionic mobility, and thus high conductivity, alternative polymer structures have been developed, for example comb-branched block copolymers such as poly[bis(methoxy ethoxy ethoxide)], usually known as MEEP. Room temperature conductivities of MEEP-based polymer electrolytes of the order of 10-5 S/cm have been achieved, values... 

The variety of branched architectures that can be constructed by the macromonomer technique is even larger. Copolymerization involving different kinds of macromonomers may afford a branched copolymer with multiple kinds of branches. Macromonomer main chain itself can be a block or a random copolymer. Furthermore, a macromonomer with an already branched or dendritic structure may polymerize or copolymerize to a hyper-branched structure. A block copolymer with a polymerizable function just on the block junction may homopolymerize to a double comb or double-haired star polymer. 

Anionic polymerization of functionalized cyclotrisiloxanes is a good method for the synthesis of well-defined functionalized polysiloxane with control of molecular mass, polydispersion, and density and arrangement of functional groups. These polymers may serve as reactive blocks for the building of macromolecular architectures, such as all-siloxane and organic-siloxane block and graft copolymers, star-, comb- and dendritic-branched copolymers and various polysiloxane-inorganic solid hybrids. 

Another embodiment of this technique was used for the synthesis of high molecular weight, low B arborescent polymers by Yuan and Gauthier in a one-pot synthesis of arborescent PSs [114]. In this case, the anionic copolymerization of styrene (Sty) and 1,3-diisopropenylbenzene (DIB) initiated by iec-butyllithium was carried out in a semibatch process. Following complete monomer conversion, the chains were terminated and the isopropenyl moieties of the DIB units were activated with xec-butyllithium to produce a polyfunctional anionic macroinitiator without additional workup. Further styrene-DIB monomer mixture additions yielded a comb-branched (GO) copolymer, and... 

Figure 9-19. A universal gel-permeation chromatography calibration curve obtained from measurements on linear poly(styrene) (O), comb-branched poly(styrene) (O ), star-branched poly(styrene) ( ), poly(methyl methacrylate) ( ), poly(vinyl chloride) (a) c -l,4-poly-(butadiene) (A), poly(styrene)-poly(methyl methacrylate) block copolymer (Qj ), random copolymer from styrene and methyl methacrylate O), and ladder polymers of poly(phenyl siloxanes) ( ) (according to Z. Grubisic, P. Rempp, and H. Benoit).

Micelle formation with amphiphilic graft and comb copolymers has received much less attention than that of block copolymers, although brush structures are gaining interest, mainly for biomedical applications (see Section 7.4). As already mentioned in Section 7.2, this is mainly due to the fact that these branched copolymers are not as well defined in structure, composition and molecular weight as the corresponding block copolymer, even if they are synthesized by controlled polymerization and macromonomer techniques. 

Figure 21.4 AFM images of isolated tetra-arm PS comb stars showing the main structural defects introduced during the synthesis (i) number of branches (ii) inhomogeneity in branch length. (Reprinted with permission from M. Schappacher and A. Deffieux, AFM image analysis applied to the investigation of elementary reactions in the synthesis of comb star copolymers, Macromolecules, 38,4942-4946,2005 2005 American Chemical Society.)...

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. 

A block copolymer contains two or more separate blocks of monomers to form a polymer with the structure poly(A-f -B) [9], where A and B are monomers and b denotes that it is a block. Copolymers can be classified according to how the monomers are arranged in the polymer structure. Linear copolymers consist of a single main chain, whereas branched copolymers consist of a single main chain with one or more polymeric side chains. Examples of branched copolymers are graft copolymers, brush copolymers and comb copolymers [10]. Block copolymers with two, three or four distinct blocks are called diblock copolymers, triblock copolymers and tetrablock copolymers, respectively, (Figure 2.4) [10]. 

Dual glass transition behavior is observed in immiscible binary polymer blends or block copolymers which have undergtme microphase separation to create discrete domains of each type of polymer in the rrratrix. The itaconate structures considered here are comb-branch polymers with relatively short side chains which plasticize the polymer efficiently when the chain lengdis are Cj to Cfy but then undergo a subtle change in bdiavior at long chain lengths. While there is no apparent... 

Two types of well defined branched polymers are acessible anionically star-shaped polymers and comb-like polymers87 88). Such macromolecules are used to investigate the effect of branching on the properties, 4n solution as well as in the the bulk. Starshaped macromolecules contain a known number of identical chains which are linked at one end to a central nodule. The size of the latter should be small with respect to the overall molecular dimensions. Comb-like polymers comprise a linear backbone of given length fitted with a known number of randomly distributed branches of well defined size. They are similar to graft copolymers, except that backbone and branches are of identical chemical nature and do not exhibit repulsions. 

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