Cationic polymerization of p-methylstyrene in selected ionic liquids and polymerization mechanism

Cationic polymerization of p-methylstyrene (p-MeSt) in imidazolium-based [NTf2−1] ionic liquids (ILs) was investigated. The effects of the anions, cations, and alkyl chain length of ILs on p-MeSt solubility and viscosity were comprehensively studied. The COSMO-RS method, which is a valuable tool for screening and selecting ILs, was also applied to identify the most suitable solvent for p-MeSt cationic polymerization. The results revealed that p-MeSt cationic polymerization proceeded in a milder exothermic manner in ILs than in a traditional organic solvent. Controlled polymerizations were achieved in [Bmim][NTf2] with a CumOH/BF3OEt2 initiating system at −25 °C when 2,6-di-tert-butylpyridine was introduced. The cationic polymerization mechanism of p-MeSt in ILs was proposed on the basis of the results of density functional theory and the terminal structures of polymers.