Effect of Associated Salts on the Polymerization of Butadiene by Organosodium Reagents

Abstract

The alfin catalyst is a combination of sodium salts which causes butadiene to polymerize at extreme rapidity in such a fashion that a greater difference exists between sodium and alfin polymerization than between sodium and emulsion polymerization. Hitherto the combination has been assumed to be binary—allylsodium and sodium isopropoxide—but a new method of preparation has revealed that a halide or pseudohalide salt is essential. Chloride, bromide, and iodide salts of sodium and potassium can be used as the halide component, but fluoride and lithium salts, as a rule, cannot be so employed unless the small size of each ion is compensated by a large cation or anion, respectively, as found in cesium fluoride or lithium iodide. The sodium cation is required for the catalyst. The potassium ion can be tolerated in the alkoxide or halide, but not simultaneousely in both. The lithium ion is in general unsuitable. Alfin polybutadiene is differentiated from sodium-polymerized butadiene by a high proportion of 1,4-structure and by an abnormally high intrinsic viscosity. Iodine chloride causes the polymer to precipitate from solution. All results indicate that polymerization by sodium reagents is in considerable degree controlled by the association of other salts with the sodium reagent.