Chemical and Biomolecular Engineering Faculty Research


Kinetic Modelling in Living Polymerizations: the Effect of Modifiers on the Degree of Polymerization in Batch and Continuous Stirred Tank Reactors

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Equations for the calculation of the degree of polymerization in 'modified' living polymerizations (living polymerizations in the presence of deliberately added terminating and transfer agents) are developed from a mechanistic/kinetic model. It is shown that a modifier, acting by the mechanism discussed, would cause more chain transfer in a continuous stirred tank reactor (CSTR) than in a batch. This is found to be the case in the living polymerization of 1,3-butadiene initiated by butyllithium in nonpolar solvents, such as cyclohexane, when 1,2-butadiene was used as a modifier. Under similar conditions no chain transfer was detected in batch polymerizations, while ≈ 20% transfer was found in a CSTR. The equations developed can be used to calculate the ratio of the rates of propagation and termination, kp/kt. CSTR data yielded kp/kt ≈ 480 at 90°C; re-evaluation of batch data published earlier by Adams et al. for the same system in hexane solvent yields kp/kt ≈ 1250 and 670 at 50° C and 70°C, respectively.

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Macromolecular Theory and Simulations





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