The cationic polymerization of 2, 4, 6-trimethylstyrene: from "truly living" to "controlled" polymers?

The cationic polymerization of 2,4,6‐trimethylstyrene in dichloromethane was initiated by the corresponding chloride with GaCl3 and BCl3 as Lewis acids. With GaCl3, the initiator, as well as the propagating ends, are fully ionized. The resulting cation appears stable from −70 to −30°C, leading to “truly living” polymers. With BCl3, the ionization is very low and the ionization constant Ki was determined (2.9 10−3 L. mol−1 at −70°C). In this case the polymerization appears perfectly “controlled”, with a good agreement between Mnth and Mnexp (up to 80000 mol.g−1) and a very narrow polydispersity. A propagation rate constant kpapp = 8500 mol. L. mol−1.s−1 was estimated at −70°C.