Kinetic Study on the Catalytic Effect of Ionic Liquids on the Polymerization of Methyl Methacrylate Co-initiated by Imine Bases
Abstract
The polymerization of methyl methacrylate (MMA) co-initiated by imine bases (IBA) is significantly accelerated by ionic liquids (ILs). IL traces added to an imine base/MMA mixture lead to both a significant decrease of the IBA polymerization activation temperature (as well as the Arrhenius activation energy) and an increase of the polymerization rate. The radical character of the polymerization is proved by copolymerization experiments of MMA with methacrylonitrile and comparison with literature known copolymerization parameters. The polymerization kinetics and temperature dependence of this process in the presence of the IL are quantified by the polymerization rate law, revealing the tremendous impact of the IL on the monomer consumption. The mechanistic interpretations are supported by DFT calculations. The activation of the IBA polymerization is strongly dependent on the IL interaction strengths with the IBA components, as suggested by correlation of kP with the empirically determined Kamlet–Taft parameters α and β of the IL. Complex interaction events are responsible for the acceleration.
