Alexandru D. Asandei, Isaac W. Moran, Gobinda Saha and Yanhui Chen
The effects of solvents, additives, ligands, and in situ drying agents as well as catalyst and initiator concentrations have been investigated in the Cp2TiCl-catalyzed radical polymerization of styrene initiated by epoxide radical ring opening. The solvents rank as follows: dioxane ≥ tetrahydrofuran > diethylene glycol dimethyl ether > anisole > diphenyl ether ≥ bulk > toluene ≫ pyridine > dimethylformamide > 1-methyl-2-pyrrolidinone > dimethylacetamide > ethylene carbonate, acetonitrile, and trioxane. Aluminum triisopropoxide and titanium(IV) isopropoxide additives lead to broad polydispersity, bipyridyl inactivates the catalyst, and triphenylphosphine improves toluene polymerizations. Lithium tri-tert-butoxyaluminum hydride, sodium borohydride, and lithium aluminum hydride form polymerization-inactive titanium hydrides, but lithium hydride, sodium hydride, and especially calcium hydride are effective as in situ trace water scavengers.