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.

The examination by 'H NMR spectroscopy at 350 MHz of commercial hydroxytelechelic polybutadienes Arco R45M@ allows the quantitative determination of the in-chain vinylcentered triads and the 4 types of hydroxylated vinyl chain ends. Vinyl primary radicals as well as macroradicals were found to propagate with penultimate and pen-penultimate effects.

SynopsisA semicontinuous emulsion process was used to polymerize vinyl acetate. The parameters studied were the rate of addition of the various ingredients. The polymerization evolution was followed as samples were taken a t regular intervals. These emulsion samples were analyzed for monomer conversion, rate of polymerization as well as for the size and the size distribution of the particles. The molecular weight and molecular weight distribution were obtained by gel permeation chromatography (GPC). Our study showed that the total surface of the particles is an important factor, that the reaction mechanism follows Krackeler's and Wessling's theory, and that the Smith-Ewart ideal case does not apply here.

Ortho-, metaand para-chloromethylstyrenes (4ac) were prepared by a three-step sequence starting from the commercial ortho-, meta-and para-br6mobenzyl bromides (la -c), which were transformed into the methoxymethyl derivatives (2ac). Coupling of the corresponding Grignard compounds with vinylbromide in presence of a transition metal catalyst led to the methoxymethyl styrenes (3a -c), which were transformed into the desired products by reaction with BC4. IR, lH and 13C NMR spectra of the 3 isomers were studied.

Isothermal emulsion polymerization at 60°C of styrene in a batch reactor were studied by using sodium lauryl sulfate as surfactant and potassium persulfate as initiator source. The concentrations of surfactant and initiator were varied during the runs. The polymerization evolution was followed as samples were taken at regular intervals. These emulsion samples were analyzed for monomer conversion, rate of polymerization, as well as for the size and the size distribution of the particles. The molecular weight and molecular weight distribution were obtained by gel permeation chromatography. Our study showed that fresh nucleation takes place even at high conversion, causing a continuous shifting toward broadening of particle size distribution. Contrary to the theory of Smith and Ewart, which assumes a constant number of particles during interval II of the polymerization reaction, our digital simulation of the reaction presents better experimental results with a variable number of particles, and indicates that the Hui–Hamielec model for termination constant kt as function of conversion is not applicable under our working conditions.