Cationic polymerization of p-methylstyrene using various metal chlorides: design rationale of initiating systems for controlled polymerization of styrenes

Cationic polymerization of p-methylstyrene (pMeSt) was examined using various metal chlorides as Lewis acid catalysts in dichloromethane. All of the catalysts used produced poly(pMeSt)s in the presence of 2,6-di-tert-butylpyridine (DTBP). However, the polymerization behavior differed depending on the type of metal chloride. The polymerization reactions conducted using SnCl4 and ZnCl2 proceeded in a controlled manner and yielded well-defined polymers, whereas metal trichlorides (for example, AlCl3, FeCl3 and GaCl3) induced uncontrolled polymerization. In addition, the combination of SnCl4 and DTBP allowed the controlled polymerization of styrene (St) and p-chlorostyrene (pClSt). Moreover, this initiating system was efficient for the synthesis of star-shaped poly(pMeSt) s via the arm-first method through the addition of an alkylstyrene-type divinyl compound used as a cross-linking agent.