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Propagation by Cationic Chain Carriers

Chain growth takes place through the repeated addition of a monomer in a head-to-tail manner, to the carbenium ion, with retention of the ionic character thronghout. [Pg.101]

The mechanism depends on the counterion, the solvent, the temperature, and the type of monomer. Reactions can be extremely rapid when strong acid initiators such as BF3 are used, and prodnce long-chain polymer at low temperatures. Rates tend to be slower when the weaker add initiators are nsed, and a polymerization with SnCl4 may take several days. Useful reaction tempraatures are in the range 170 to 190 K, and both molar mass and reaction rate decrease as the temperature is raised. [Pg.101]

Propagation also depends greatly on the position and type of the gegen ion assodated with the chain carrier. The position of the gegen ion can be altraed by varying the dielectric constant of the solvent, and large changes in can be obtained [Pg.101]

It has been suggested that the various stages of the ionization prodneing carbenium ions can be represented as [Pg.101]

Cationic Polymerization of Styrene in Media of Varying Dielectric Constant e [Pg.102]


See other pages where Propagation by Cationic Chain Carriers is mentioned: [Pg.101]   


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