Cationic polymerization of styrene by the TiCl4/N,N,N′,N′-tetramethylethylenediamine(TMEDA) catalyst system in benzotrifluoride, an environmentally benign solvent, at room temperature

Abstract

Highly efficient carbocationic polymerization of styrene was achieved under environmentally advantageous conditions in benzotrifluoride, BTF (α,α,α-trifluorotoluene, TFT), an environmentally benign solvent at room temperature, that is without any energy consumption for cooling or heating, with even better yields than that in the usually applied volatile and harmful, widely used chlorinated solvent, dichloromethane (DCM). The polymerization was initiated by 1-phenylethyl chloride in conjunction with the TiCl4/TMEDA (N,N,N′,N′-tetramethylethylenediamine) catalyst (coinitiator) system. Within a very short reaction time (5 min), higher conversion values were obtained in BTF (89%) than in DCM (76%), that is the TiCl4/TMEDA combination proved to be a powerful catalyst for the carbocationic polymerization of styrene even in BTF. The molecular weight distributions of the synthesized polymers were relatively narrow in both solvents (Mw/Mn = 1.29–1.65). The effect of the increasing reaction temperature (up to room temperature) was also investigated. With increasing reaction temperature, the polydispersity decreased and Mn close to the theoretical one was obtained in BTF at room temperature. Structural analysis with 1H NMR revealed that the major chain breaking reaction in this polymerization is indanyl ring formation between the penultimate monomer unit and the propagating carbocation. These results indicate that BTF can be utilized as a unique, inert, non-volatile, environment friendly solvent with medium polarity for cationic polymerization of styrene, a nonfluorous monomer, and based on these results, presumably it may be also applied effectively as a quite universal solvent for a large array of various polymerizations and copolymerizations for not only fluorinated, but also for nonflourous monomers, and other chemical reactions as well.