Polyisoprene using free radical catalyst

Further evidence for the hypothesis was found in the patent describing the isoprene—acrylonitrile—zinc chloride system (23). On adding a four-fold excess of isoprene to an equimolar mixture of acrylonitrile and zinc chloride, in the absence of a free radical catalyst, an exothermic reaction occurs after approximately 30 minutes. The recovered polymer is insoluble in hydrocarbons, chloroform, and acetone. This eliminates polyisoprene and the alternating copolymer. The yield of product is 12%, calculated a polyacrylonitrile, compared with the 16.8% yield of copolymer obtained when excess acrylonitrile and a free radical catalyst are used. 

Synthetic polyisoprene, prepared by free-radical polymerization of isoprene monomer, is a copolymer of six structurally distinct kinds of isoprene chain units. Unlike natural rubber, which is a regularly repeating Class I structure (cis-1,4), such synthetic polyisoprene does not crystallize. On the other hand, by the use of the appropriate stereospecific catalyst, isoprene monomer can be converted to a regular Class I polymer with the same structure as natural rubber (. ... 

PREPARATIVE METHODS ds-l,4-Polyisoprene is made by coordination, anionic, free-radical, or cationic polymerization of isoprene through the use of coordination catalysts, alkali metal catalysts, AUin catalysts, organoalkani catalysts, or conventional Lewis acids. ... 

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