N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide as counter radical in the controlled free radical polymerization of styrene: kinetic aspects

The controlled free radical polymerization of styrene with N-tert-butyl-1-d iethylphosphono-2,2-dimethylpropyl nitroxide (DEPN) as counter radical was studied. Polymerizations were performed in bulk, with a DEPN-capped polysty ryl as alkoxyamine initiator, in the presence of an excess of DEPN nitroxyl free radicals. Kinetics of the polymerization were followed at 115 degrees C, 125 degrees C and 130 degrees C. The equilibrium rate constant K = k(d) /k(c) of exchange between dormant and active species was determined experim entally from the slope of Ln([styrene]0/[styrene]) versus time. The obtaine d Arrhenius relation was the following: K(mol . L-1) = 1.45 x 10(7) exp (-1 13.5 kJ . mol-(RT)-R-1/), i.e., K = 1.9 x 10(-8) mol . L-1 at 125 degrees C . This result is consistent with a much faster polymerization of styrene wi th DEPN than with Tempo as nitroxyl counter radical (K = 2.1 x 10(-11) mol . L-1 at 125 degrees C determined previously by Fukuda).