SynopsisAs a part of a program involving synthesis of various rubbers, the stereospecific polymerization of butadiene waa studied. A Ziegler catalyst composed of cobaltous chloride, triethyl aluminum and aluminum chloride in benzene waa used. The effect of catalyst age on stereospecificity of the polymers produced was observed over a period of nearly two years. Freshly prepared catalyst appears aa a straw-yellow liquid over black insoluble solids. Within a few weeks a black separate liquid phaae begins to form at the bob tom of the catalyst. The amount of the dark lower layer increase8 on standing until all of the solids have been dissolved. Polymers prepared from the upper layer of catalyst showed decreasing percentages of eis-double bonds, an effect which waa linear up to approximately one year. From one to two years, the upper layer produced polymers which were essentially constant at 70% cis-olefinic bonds. In contrast, the dark lower layer of catalyst yielded polymers which were high in &-content (greater than 95% cis-bonds) over the entire period of the study.
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