The carbo-cationic polymerization of styrene has been studied in a Spinning Disc Reactor (SDR) and the results were compared to those observed in a conventional Stirred Tank Reactor (STR). Addition of styrene to a slurry of silica-supported boron trifluoride (BF3/SiO2) in 1,2-dichloroethane led to uncontrollable reactions in the STR at monomer concentrations > 25%w/w and initial temperatures of 20-25 degrees C. By comparison, monomer concentrations of 75%w/w were safely and controllably polymerized in the SDR at 40 degrees C to yield polymers with molecular weights comparable to those reported in the literature for polymer prepared at -60 degrees C. Exceptional heat transfer rates achieved in the SDR are sufficient to deal with the heat evolved when styrene is polymerized at concentrations as high as 75%w/w, the reaction proceeding under essentially isothermal conditions. In the present study, the effects of monomer/solvent feed rates, monomer concentrations, disc size, and disc speed on monomer conversions, polymer molecular weights, and polydispersities achieved in the SDR are investigated. Speculative explanations of the observed results are presented in terms of enhanced mixing effects on the polymerization mechanisms in the SDR. (c) 2006 Wiley Periodicals, Inc.