Chemical and Biomolecular Engineering Faculty Research

Title

Kinetics of the Carbocationic Homopolymerization of Isobutylene with Reversible Chain Termination

Document Type

Article

Publication Date

1994

Abstract

The kinetics of isobutylene (IB) polymerization, initiated by 2-chloro-2,4,4-trimethylpentane (TMPCI)/TiCI4 initiator/coinitiator system in methyl chloride/methyl/cyclohexane solvent mixture at −90°C, was investigated. The existence of a dynamic equilibrium between dormant and active species was verified by obtaining ‘living’ conditions and 100% initiator efficiency using a large excess of initiator over coinitiator [TMPCI]0 >> [I]4. It was shown that the polymerization rate is first order in monomer and is directly proportional to [TiCI4]0 and [TMPCI]0. From polymerization rate data the overall polymerization rate constant k′p=kpK1 was calculated, where kp is the rate constant of propagation and K1 = k1/k−1 is the equilibrium constant for the dormant-active species equilibrium. The rate of TMPCI consumption was shown to be first order in [TMPCI]. While polymer concentration increased during the rather slow initiator consumption, the polymerization rate did not accelerate as the concentration of active species, determined by the dormant-active species equilibrium, remained constant. From initiator consumption data k1 and kp/k−1 values were estimated. The estimated rate constant values were used to simulate monomer and initiator conversion histories versus time. The simulated histories were in good agreement with measured data.

Publication Title

Polymer Reaction Engineering

Volume

2

Issue

3

First Page

251

Last Page

273