(79d) Synthesis of Medium Molecule Weight Polyisobutylene at Elevated Temperature in Microreactor

The medium molecule weight polyisobutylene (PIB, Mn=50000~100000) obtained by cationic polymerization has broad application fields such as adhesives, sealants, lubricating oil modifier and chewing-gum. The aluminum chloride (AlCl₃) is a cost effective co-initiator in the cationic polymerization, but suffers from extremely high and moisture sensitive reactivity out of controllability of batch reactor under mild reaction temperature. Exploring the window towards the synthesis of PIB at elevated temperatures for facile production and product development has considerably academic and technological significances. We envisage that using microflow system may open the access due to excellent controllability based on enhanced mixing and exact residence time. In this work, using AlCl₃/H₂O as initiation system and dichloromethane as diluent, we confirms the generation of medium molecule weight PIB with narrow molecule weight distribution is remarkably conducted within 1 s at 273.15 K in a microflow device. Due to the high mixing intensity, the effects of temperature, coming from dynamic profile of reaction system composition as considerable polymerization taking place, are weakened. The short residence time inhibits polymer chains or initiator species participate in reaction in turns. Thereafter, the calculation on initiator species concentration is realized to reveal the complicated interaction between AlCl₃ and H₂O in chain reaction, and calibrate the chain length according to the balance between chain propagation factor and chain termination factor. The attainment of PIB with specific molecule weight succeeds by reaction system composition control finally. This work provides the possibility to achieve reliable, designable, and continuous PIB production at elevated temperature.