FREE-RADICAL INITIATION MECHANISMS IN THE POLYMERIZATION OF DIETHYL FUMARATE AND DIETHYL MALEATE STUDIED BY THE NITROXIDE TRAPPING TECHNIQUE

The radical trapping technique employing the stable nitroxide 1 as a s cavenger has been used to study the reaction of t-butoxyl radicals wit h diethyl fumarate and with diethyl maleate. The major pathway with bo th monomers is hydrogen abstraction from the ester alkyl groups by t-b utoxyl radicals. The addition of t-butoxyl radicals to monomer is of m inor importance. At low nitroxide concentrations, addition of the seco ndary hydrogen abstraction radical to monomer is competitive with trap ping by the nitroxide. This suggests that the initial propagation rate constant is much greater than the overall average propagation rate co nstant for homopolymerisation of these monomers.