KINETIC-MODEL FOR FREE-RADICAL ADDITION-FRAGMENTATION ASSOCIATED WITHINITIATION AND PRIMARY RADICAL TERMINATION

A kinetic model has been proposed for a free-radical polymerization in the presence of an added initiator and an addition-fragmentation agen t. The present one is considered as a special case where the addition- fragmentation agent acts also as an initiator. The model takes into ac count the chain termination process by way of primary radicals and exc ludes the mutual termination of primary radicals. The general model ha s been applied to the case of methyl methacrylate (MMA) polymerization in the presence of a peroxyketal, viz., ethyl 2-[((1-n-butoxyethyl)pe roxy)ethyl]propenoate (EBEPEP) as the addition-fragmentation agent. An expression for the molar mass of the formed polymer has also been der ived considering the various initiation and termination processes as a n improvement over the conventional Mayo equation. The kinetics were p erformed at various temperatures to prove the validity of the equation , and the different kinetics factors relevant to initiation, addition- fragmentation, and primary radical termination were evaluated. The add ition-fragmentation agent in this case manifested retardation until 70 degrees C beyond which the polymerization rate increased with increas e in concentration of addition-fragmentation agent caused by the therm al decomposition of the peroxy group on EBEPEP.