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This work investigates a dual Lewis acid catalytic system for synthesizing low-molecular weight polyisobutylene.

June 26, 2026Open Access

Experimental and Theoretical Studies on the Polymerization of Isobutylene Using the GaCl3-Based Catalytic System

XYXinyi YangEast China University of Science and Technology XFXindi FengEast China University of Science and Technology JCJiongyi ChenNational University of Defense Technology

Key Points

This work investigates a dual Lewis acid catalytic system for synthesizing low-molecular weight polyisobutylene.
Utilized GaCl3·AlCl3/H2O dual catalytic system for reaction optimization.
Conducted density functional theory (DFT) calculations to analyze reaction mechanisms.
Measured conversion rates and molecular weights of polyisobutylene produced.
Achieved 97% conversion of isobutylene monomer with a number average molecular weight of 3900 g/mol.
DFT calculations showed a lower proton transfer barrier of 5.8 kcal/mol in the dual catalyst compared to GaCl3/H2O.
The dual system demonstrated enhanced interaction and positive electrostatic potential, improving catalytic performance.

Abstract

This work investigates a novel GaCl3·AlCl3/H2O catalytic system for the synthesis of low-molecular weight polyisobutylene (LPIB). Catalytic performance was improved by employing a dual Lewis acid system, which outperformed the conventional single component (GaCl3/H2O) catalyst in terms of both reaction rate and yield. In accordance with the optimized reaction conditions, the conversion of monomer was found to be 97%, thereby achieving low molecular weight polyisobutylene (LPIB) with a number average molecular weight (Mn) of 3900 g/mol. Density functional theory (DFT) calculations revealed a lower proton transfer barrier (5.8 kcal/mol) in the dual Lewis acid catalytic structure compared to its single component counterpart. Subsequent theoretical analyses, incorporating electrostatic potential (ESP), independent gradient model based on Hirshfeld partition (IGMH), and distortion/interaction analysis, attributed this observed kinetic advantage to a higher positive ESP extremum and enhanced interaction between the IB fragment and the Lewis-acidic active center. Together, these results establish the GaCl3·AlCl3/H2O dual Lewis acid system as an enhanced catalytic platform over the conventional GaCl3/H2O system for efficient IB polymerization toward LPIB synthesis.

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