By PMR, three dioxane–Li+ complexes have been detected for the oligopolyisoprenyl–lithium–dioxane mixtures in benzene solution. The (4‐1) living end isomerizes into the cis configuration when the sample temperature or the dioxane concentration is increased, but the isomerization phenomenon is reversible only if dioxane/Li+ ratios are smaller than unity. The specificity of the vinyl addition (86%), mainly (4‐3) (70%), due to the stronger negative charge at the Cγ carbon atom is effective only at low temperature (+15°C). At higher temperature, because of the steric hindrance of the methyl group, this stereospecificity decreases.
SynopsisGraft copolymers of PVCg-PS of controlled branching were prepared by carbanionic deactivation.It appears that secondary reactions affect the efficiency of the grafting, chiefly at low ratios of polystyrene to poly(viny1 chloride). Techniques of grafting and analyses are discussed.The reaction products were characterized mainly by GPC.
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