Poly living polymer

Ion coupling of anionic and cationic living polymers is an interesting procedure for the synthesis of a well-defined block copolymer. Attempted coupling of the polystyrene anion with the poly-THF cation initiated by triethyloxonium tetrafluoro-borate yielded a block copolymer mixed with homopolymers394. The block ef-... 

The observations discussed above suggest that the kinetic order of lithium poly-isoprene propagation should vary with the living polymer concentration. The effect is imperceptible in aliphatic hydrocarbons, but is observed in benzene solutions. The apparent propagation constants of lithium polyisoprene (MW 2 2 10 ) were determined in benzene and the results are displayed in Fig. 16 in the form of a plot of log kapp vs log c, c denoting the total living polymer concentration. 

Similar divergences are found for lithium poly-2,4-hexadiene solution (1 10-3 M in living polymers) for which a sixfold decrease of viscosity upon protonation corresponding to a degree of association of 1.7 was reported 113), whereas only a threefold decrease, i.e. a degree of association of 1.4 was indicated earlier 1,8). The difference between the 1.7 and 1.4 values was tentatively attributed to a slow decomposition of the active ends over a period of two weeks U8) notwithstanding their reported good... 

Poly (alkyl methacrylate) macromonomers are formed by reaction of the living polymer with VBC. This method was shown to be free of side reactions and quantitative, in spite of the low nucleophilicity of the carbanionic site involved 72,75). 

The polydispersity of polymers prepared in this way is usually very low for example, a value MJM of 1.05 was found for a sample of poly(a-methylsty-rene). Living polymers can also be used for the preparation of block copolymers after the consumption of the first monomer, a second anionically polymerizable monomer is added which then grows onto both ends of the initially formed block. By termination of the living polymer with electrophilic compounds the polymer chains can be provided with specific end groups for example, living polystyrene reacts with carbon dioxide to give polystyrene with carboxylic end groups. 

Kl1/2 K3[(Li+,poly-dienyl-)2]1/2 >9> 1 the rate becomes proportional to 1/4 power of living polymers concentration. Since is large while is very small, both... 

Let me pass now to some problems of co-polymerization of lithium salts of living polymers. With Dr. Zdenek Laita we studied the rate of cross-over reaction converting lithium poly-styryl into 1,1-diphenyl ethylene", D end-groups in benzene(23). The stoichiometry of the reaction is... 

Figure 2. Effect of deactivation on viscosity of a living solution in THF of poly(2-vinylpyridine) MgBz prepared from dibenzylmagnesium living polymer...

In block copolymerization, the second step is also ionically catalyzed. However, it is possible for the living homopolymer to react with a peroxide initiator first and to complete the process by free-radical polymerization. R. B. Seymour and co-workers carried out both steps by free-radical polymerization. They obtained live polymers in free-radical solution poly-... 

A cyclic polymer of methyl methacrylate was also synthesized using a het-erotelechelic polymer precursor, although the formation of living polymer of methyl methacrylate is more difficult than that of styrene. Mizawa et al. described the synthesis of heterotelechelic poly(methyl methacrylate) containing a-maleimide-tw-dienyl end groups and its intramolecular cyclization... 

The structure of the live lithium chain ends is a matter of controversy and will be discussed in a later section. After the lithium-polybutadiene is terminated with protic material, the isolated poly butadiene polymer exhibits a mixed microstructure (—35% cis-1,4, 54% trans-1,4, and -11% 1,2). 

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