Kinetics of heterogeneous atom transfer radical polymerization of methyl methacrylate

A new kinetic equation for copper-mediated ATRP is introduced based on the exptl. observation that the deactivator concn. ([CuII]) remains const. throughout the polymn. This const. deactivator concn. can originate from the use of a heterogeneous transition metal/ligand system, resulting in the pptn. of deactivating species when the concn. exceeds a ceiling concn. Equations are derived in which the decrease of the radical concn. in time is assigned to the decrease of the concn. of the activator and the dormant chains. When the equil. const. is low and/or the polymn. rate high, the radical concn. remains const. up to high conversions indicating little termination. In the case where a monomer is used with a high equil. const. and a relatively low polymn. rate, the radical concn. is continuously decreasing in time, as the concn. of both the activator and the dormant species is decreasing throughout the polymn. To validate the kinetic equation, polymn. of Me methacrylate was performed with an alkyl bromide initiator and a heterogeneous CuIBr/CuIIBr2/PMDETA system. ESR spectroscopy was used to demonstrate that the deactivator concn. remains const. throughout the polymn. Simulations and exptl. results are in very good agreement. [on SciFinder (R)]