Abstract
AbstractThe stereoregularity of polystyrenes obtained with sodium, potassium, rubidium, and cesium naphthalenes in various solvents was determined by 13C‐NMR spectroscopy. Polystyrenes produced by contact ion pairs of polystyryl cesium in dioxane and tetrahydrofuran (THF) had the proportions of a 57–58% racemic dyad (Pr), whereas the Pr values increased to 65 and 69% by solvating Cs+ counterions in dimethoxyethane and by agent‐separating them with crown ether, respectively. Polystyrene obtained by contact ion pairs of polystyryl sodium in dioxane showed a Pr of 66%; polymers produced by solvent‐separated ion pairs of polystyryl sodium in THF at −78°C had a Pr of 71%. A polymerization system which contained alkali counterions with large ionic radii and solvents with low dielectric constants in which only contact ion pairs existed produced polystyrenes with isotactic‐rich configurations. The stereoregularity of polystyrene produced by contact ion pairs of polystyryl potassium and rubidium in tetrahydropyran (THP) occurred intermediately between that of polymers obtained in diethyl ether and THF. It was concluded that the stereoregulation of contact ion pairs may be closely related to the interionic distance of the ion pair.
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