Kinetic modelling in living polymerizations: The effect of modifiers on the degree of polymerization in batch and continuous stirred-tank reactors

✍ Scribed by Puskas, Judit E.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1993
• Weight: 310 KB
• Volume: 2
• Category: Article
• ISSN: 1018-5054
• DOI: 10.1002/mats.1993.040020110

✦ Synopsis

Abstract

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, k~p~/k~t~. CSTR data yielded k~p~/k~t~ ≈ 480 at 90°C; re‐evaluation of batch data published earlier by Adams et al. for the same system in hexane solvent yields k~p~/k~t~ ≈ 1250 and 670 at 50° C and 70°C, respectively.