Viscosity effects on the thermal decomposition of bis(perfluoro-2-N-propoxypropionyl) peroxide in dense carbon dioxide and fluorinated solvents.
The thermal decomposition of the free-radical initiator bis(perfluoro-2-N-propoxyprionyl) peroxide (BPPP) was studied in dense carbon dioxide and a series of fluorinated solvents. For the fluorinated solvents, the observed first-order decomposition rate constants, k(obs), increased with decreasing solvent viscosity, suggesting a single-bond decomposition mechanism. The k(obs) values are comparatively larger in dense carbon dioxide and similar to the "zero-viscosity" rate constants extrapolated from the decomposition kinetics in the fluorinated solvents. The decomposition activation parameters demonstrate a compensation behavior of the activation enthalpy with the activation entropy upon change in solvent viscosity. Comparison of the change in activation parameter values upon change in solvent viscosity for BPPP with two additional initiators, acetyl peroxide (AP) and trifluoroacetyl peroxide (TFAP), further suggests that carbon dioxide exerts a very minimal influence on the decomposition mechanism of these initiators through solvent-cage effects.
Bunyard
W C
WC
National Science Foundation Science and Technology Center for Environmentally Responsible Solvents and Processes, Department of Chemistry, University of North Carolina at Chapel Hill, CB 3290, Chapel Hill, North Carolina 27599-3290, USA.
Kadla
J F
JF
DeYoung
J
J
DeSimone
J M
JM