Issue 18, 2017

Synthesis of highly reactive polyisobutylene by catalytic chain transfer in hexanes at elevated temperatures; determination of the kinetic parameters

Abstract

The kinetics and mechanism of the polymerization of isobutylene (IB) using an ethylaluminum dichloride (EADC)·bis(2-chloroethyl) ether (CEE) complex as a catalyst in conjunction with tert-butyl chloride (t-BuCl) as an initiator in hexanes at 0 °C have been previously reported. In an effort to further study the catalyst performance, we have investigated the polymerization at elevated temperatures. Polymerization rates increased while molecular weights and exo-olefin contents (90–78%) decreased with increasing temperature. At elevated temperatures the first-order plots are curved upward, suggesting that the formation of the tert-butyloxonium ion is slower at higher temperatures. 1H NMR studies confirmed that the t-butyloxonium ion is stable up to 15 °C but slowly decomposes at 20 °C. Linear first order plots were obtained when the polymerization was carried out with the tert-butyloxonium ion preformed at 10 °C. The slope of the first order plots that is proportional to the steady state concentration of carbenium ions increased 2, 3 and 4 fold at 10, 15 and 20 °C relative to that at 0 °C. Kinetic parameters of activation–deactivation were determined using model reactions. The rate constant of activation at 0 °C (ka = 3 × 10−4 s−1) increased 2, 3.4 and 4 fold at 10, 15 and 20 °C, respectively, in line with the rate increases. The deactivation rate constant, kd = 1010 L mol−1 s−1 was at the diffusion-limit.

Graphical abstract: Synthesis of highly reactive polyisobutylene by catalytic chain transfer in hexanes at elevated temperatures; determination of the kinetic parameters

Supplementary files

Article information

Article type
Paper
Submitted
10 Mar 2017
Accepted
09 Apr 2017
First published
10 Apr 2017

Polym. Chem., 2017,8, 2852-2859

Synthesis of highly reactive polyisobutylene by catalytic chain transfer in hexanes at elevated temperatures; determination of the kinetic parameters

T. Rajasekhar, J. Emert and R. Faust, Polym. Chem., 2017, 8, 2852 DOI: 10.1039/C7PY00415J

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements