Cyanoprene radical polymerizations

Besides the 1,4- and 3,4-adducts, cyclic structures are also present. Four representative radical polymerizations of cyanoprene are compared in Table I. Differential thermal anlysis shows, for the material made from toluene, a glass stage of about 10°C and a melting range above 90°C. The material has medium crystallinity while the material made in THF is largely amorphous. 

Anionically Initiated Polymerization. The disadvantages of radical polymerization of cyanoprene result from the operating conditions (temperatures) too many side reactions, chain-terminating reactions, and consecutive reactions occur. Because of this and the dimerization tendency of cyanoprene, catalysts had to be found that could fulfill two contradictory requirements. They should be so reactive that it would be possible to work at temperatures that exclude dimerizations as com-... 

Coordinate Homopolymerization. When Ziegler-Natta catalysts of the type TiCl4/alkylaluminum compounds are used, no polymerization occurred because the cyanoprene (like acrylonitrile for instance) reacts with the catalyst and destroys it. Polymerization occurs, however, when metal acetyl acetonates and organoaluminum compounds are used. For example, coordinate polymerization with a mixture of cobalt acetyl acetonate and ethylaluminum dichloride results in a polymer that corresponds mainly to the radical-produced polymer. 

The expressions are an outcome of the terminal model theory with several steady-state assumptions related to free-radical fiux (14,23). Based on copolymerization studies and reactivity ratios, chloroprene monomer is much more reactive than most vinyl and diene monomers (Table 1). 2,3-Dichloro-l,3-butadiene is the only commercially important monomer that is competitive with chloroprene in the free-radical copolymerization rate. 2,3-Dichlorobutadiene or ACR is used commercially to give crystallization resistance to the finished raw polymer or polymer vulcanizates. a-Cyanoprene (1-cyano-l,3-butadiene) and /3-cyanoprene (2-cyano-1,3-butadiene) are also effective in copolymerization with chloroprene but are difficult to manage safely on a commercial scale. Acrylonitrile and methacrylic acid comonomers have been used in limited commercial quantities. Chloroprene-isoprene and chloroprene-styrene copolymers were marketed in low volumes during the 1950s and 1960s. Methyl methacrylate has been utilized in graft polymerization particularly for vinyl adhesive applications. A myriad of other comonomers have been studied in chloroprene copolymerizations but those copolymers have not been used with much commercial success. 

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