Cationic polymerization of isobutylene by AlCl3 in n‐hexane and toluene at mild temperatures

Abstract

This study aims to find more efficient ways to manufacture highly reactive polyisobutylene (HRPIB) and modified conventional PIB materials (MCPIB) industrially with high vinyl exo‐group contents through cationic polymerization at mild temperatures. The study performed polymerizations using aluminum trichloride (AlCl3) as a catalyst with different nonpolar solvents (hexane and toluene), reaction temperatures (10 and 30°C), and co‐catalysts (water and dibutyl ether [DBE]). At 30°C, toluene can provide vinyl contents above 30 mol%. Particularly, an important synergetic effect was observed between toluene and ether, as corroborated by statistical analyses, resulting in vinyl contents above 50 mol%, while reactions performed in n‐hexane provided maximum vinyl content of 20 mol%. In all cases, number average molar masses ranged from 200 to 1000 Da, which are typical of CPIB and MCPIB materials. Moreover, addition of excess of ether indicated the likely inhibition of reaction rates in presence of high ether concentrations (≥1.18 × 10 ⁻¹ mol/L). The obtained results indicated that AlCl3 can be used successfully to manufacture MCPIB products with terminal vinyl contents above 50 mol% at mild temperatures in common nonpolar solvents (n‐hexane and toluene) and in presence of common co‐catalysts (water and DBE) with high rates of reactions.