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Star-shaped polymers living

The synthesis of tailor-made star-shaped polymers can be performed in several ways by means of a plurifunctional organometallic initiator, or by reacting a living precursor polymer with a plurifunctional reagent, to build the centra] body, or by block copolymerization involving a diunsaturated monomer (Scheme 3). [Pg.161]

The star-shaped polymers were prepared by the addition of the DVB solution to the "living polydienyllithium hexane solution. Prior to the addition of divinylbenzene (DVB), a portion of the linear polymer solution was isolated via the sidearm, which enabled the arm molecular weight to be determined. [Pg.561]

A method for preparing star-shaped polystyrene by either the incremental or single addition of divinyl benzene to a living polystyryl anion is described. Star-shaped polymers containing up to 34 arms were prepared with polydispersities of less than 1.1. [Pg.417]

Other synthetic possibilities provided by the living polymer technique may permit syntheses of star-shaped polymers, uniform networks of cross-linked polymers, regular branched polymers, etc. [Pg.97]

Coupling Reaction 5b involves reacting living A-B polymer chains with divinylbenzene (DVB). The polymerization of DVB then results in a hub containing pendent vinyl groups that serve as branch points for the star-shaped polymer. This procedure has led to the... [Pg.188]

Living polyTBA with Mn = 5,500 formed a star-shaped polymer containing up to five branches upon coupling with diethylenetriamine 113,126) ... [Pg.283]

As discussed in Chapter 7, the absence of termination in living polymerization permits the synthesis of unusual and unique block polymers — star- and comb-shaped polymers. Living polymerization can also be employed to introduce a variety of desired functional groups at one or both ends of polymeric chains both in homo- and block polymers. In particular, living polymerization techniques provide the synthetic polymer chemist with a vital and versatile tool to control the architecture of a polymer complicated macromolecules can be synthesized to meet the rigid specification imposed by a scientific or technological demand. [Pg.45]

GTP constitutes an example of Michael addition polymerization involving the addition of a silyl ketone acetal to a,p-unsaturated carbonyl compounds in the presence of a nucleophilic or Lewis acid catalyst Due to the living nature of GTP, the method was applied successfidly to the synthesis of well-defined random, block-graft, star-shaped polymers as well... [Pg.525]

In these two decades remarkable progress has been made in the development of excellent catalysts for living and stereospecific acetylene polymerizations (10,26-28). The r-conjugated polymers prepared by the sequential polsrmerization are strictly limited to polyacetylenes, except for only a few examples. Thus, synthesis of tailor-made conjugated macromolecules such as end-functionalized polymers, block copolymers, star-shaped polymers is possible only in the case of substituted acetylenes. [Pg.18]

Figure 3.1 Synthesis of sequence-controlled pol3uners by living cationic polymerization. (A) Copolymers containing acid-degradable acetal units. (B) Block copolymers with an acid degradable segment. (C) and (D) Synthesis of star-shaped polymers with acid-degradable acetal units in the core. Figure 3.1 Synthesis of sequence-controlled pol3uners by living cationic polymerization. (A) Copolymers containing acid-degradable acetal units. (B) Block copolymers with an acid degradable segment. (C) and (D) Synthesis of star-shaped polymers with acid-degradable acetal units in the core.
Star-shaped poly(IBVE) was obtained in 100% yield [276] from the living polymer reaction (DPn = 50-300) of IBVE, prepared with IBEA/EtAlCl2 at 0 C in hexane in the presence of ethyl acetate, with a small amount of 1,4-cyclohexanedimethanol divinyl ether. A notable feature of these starshaped polymers was their extremely narrow MWDs (Mw/Mn = 1.1-1.2) [276]. To the best of our knowledge, this was the first example of selective preparation of star-shaped polymers with a narrow MWD in quantitative yield, which had never before been achieved even with other polymerization mechanisms. The Mw ranged from 6 x 10" to 30 x 10, and each polymer molecule had between 9 and 44 arms. [Pg.198]

In the case of the application of p-divinylbenzene for this purpose the core macromolecule is a cross-linked polymer. Despite that the presence of long, linear arms, derived from the living polymer makes the macromolecule soluble. It turned out that not all active centers in the cross-linked core of poly divinylbenzene are accessible in the same way. For this reason the initiation of the reaction proceeds slowly and leads to the star-shaped polymer with arms of different lengths. An important advantage of this method is the possibility to obtain the star block copolymers. An example of such a compound is a copolymer containing up to 30 arms. Each of them is a block copol5mer of st3Tene (M = 2700-30,000) and ethylene oxide (M = 3000-6000). In addition to this information it should... [Pg.297]


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See also in sourсe #XX -- [ Pg.46 , Pg.49 , Pg.81 ]




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