Cp2 TiCl-Mediated Controlled Radical Polymerization of Isoprene Initiated by Epoxide Radical Ring Opening

The effect of the reaction variables in the Cp 2 TiCl-mediated controlled radical isoprene polymerizations initiated by epoxide radical ring opening was investigated over a wide range of conditions ([Cp 2 TiCl 2 ]/[ epoxide] = 1/1-6/1, [Cp 2 TiCl 2 ]/[Zn] = 1/0.5-1/8, [isoprene]/[epoxide] = 20/1-1000/1, T = 70-130 °C in THF and dioxane), to reveal a linear dependence of molecular weight on conversion, linear kinetics and moderate polydispersities up to high conversions, with an optimum in initiator efficiency, rate and polydispersity for [epoxide]/[Cp 2 TiCl 2 ]/[Zn] = 1/3/6-1/4/8 at 90 - 110 °C. NMR studies demonstrated the epoxide initiation and the stereoselectivity of a conventional radical polymerization. Furthermore, random and block copolymers with styrene could also be obtained.