Fast flow synthesis of highly reactive polyisobutylene co-initiated by an AlCl3/isopropyl ether complex

Abstract

In this work, with AlCl₃ addition in the range from 4 to 10 mmol L⁻¹ and enough isopropyl ether (ⁱPr₂O) addition, we successfully synthesized highly reactive polyisobutylene (HRPIB) using a microflow system within 12 s or less. The temperature window was extended from −20 °C to 50 °C, and the molecular weight (M_n) was adjustable between 500 and 15 000. The evolutions of HRPIBs and the effects of reaction conditions were carefully investigated, revealing multiple effects of an excess of ⁱPr₂O over AlCl₃ including: (1) decreasing the intensive isomerization co-initiated by free AlCl₃; (2) inhibiting the chain termination to present chain transfer dominated kinetics; (3) weakening the temperature sensitivity of M_n as a restriction on temperature elevation; (4) retarding the chain propagation to slow the reaction and increase the probability of isomerization. Key access to fast synthesis of high quality HRPIB is proposed to make a compromise of these effects by properly selecting ⁱPr₂O : AlCl₃.