By L. J. Ferry
This exhaustive reference textual content systematically introduces the fundamental theories and experimental equipment of anionic polymerization in addition to the synthesis, research, and features of anionically polymerized items.
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As noted before in this review, the equilibrium constant for the process shown in Eq. 5 LM -1, which is in sharp contrast with the value of about 160 LM -~ found for the THF-poly(styryl)lithium system. The possibility of comptexation of T H F directly with the poly(isoprenyl)lithium aggregates, Eq. (13), was not considered by Morton and Fetters 47) Davidjan et. al. 01). , the non-associated active center. A clear consensus 47,156,166) has emerged which indicates that various extents of ether complexation with active centers can reduce their reactivity in the chain propagation event.
This could involve as much as about 10~ of the active centers, but the cyclic structure so formed, if associated, would exhibit a dimeric or greater degree of aggregation. As has been mentioned, Worsfold 133~ has suggested that the rate of association-dissociation may be altered so that chain "entanglements" may be removed by one chain slipping through the gap transiently open between associating active ends. The effect, if such a mechanism exists, would be to cause a drop in viscosity. In the present case, the reduction in the mean lifetime of a dimeric aggregate could arise from the 40 R .
Below this temperature the absorption maximum moves to longer wavelength corresponding to the preferential formation of the trans species. The difference between the absorption maxima of the cis and trans ions is quite small, viz. 287 and 305 nm, respectively. Allowing a solution of poly(isoprenyl)lithium in THF to warm to 30 °C results in a chemical change to a species having a broad asymmetric absorption band with a maximum near 330 nm. This process was retarded bythe presence of lithium tetraphenylborate -- presumably by suppressing dissociation into the free carbanion.