Butadienes, magnesium-based catalyst

Table 11 Polymerization of butadiene with magnesium-based catalyst mixtures (adopted from [181])...

The stereoregularity of butadiene based polymers prepared in cyclohexane with Ba-Mg-Al catalysts depends on polymerization temperature and catalyst concentration. Trans-1,4 content increases nonlinearly with a decrease in polymerization temperature over the range of 80° to 30°C (Figure 11) and/or a decrease in the initial molar ratio of butadiene to dialkyl-magnesium from 3400 to 400 (Figure 12). For polybutadienes prepared with relatively large amounts of catalyst at 30°C, the trans-1,4 content approaches a limiting value of about 907.. 

Langer (13) has also disclosed the use of alkyllithium and dialkyl-magnesium tertiary diamine complexes as catalysts for copolymerization of ethylene and other monomers such as butadiene, styrene, and acrylonitrile to form block polymers. Examples are given in which polybuta-dienyllithium initiates a polyethylene block, as well as vice-versa. Random copolymers of these two were also prepared, and other investigators have used not only tertiary diamines but hexamethylphosphoramide (14) and tetramethylurea (15) as nitrogenous base cocatalysts in such polymerizations. Antkowiak and co-workers (11) showed the similarity of action of diglyme and TMEDA in copolymerizations of styrene and... 

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