CHAIN TRANSFER BY ADDITION SUBSTITUTION FRAGMENTATION MECHANISM .1. END-FUNCTIONAL POLYMERS BY A SINGLE-STEP FREE-RADICAL TRANSFER-REACTION - USE OF A NEW ALLYLIC LINEAR PEROXYKETAL

A new chain transfer agent, ethyl 2-[1-(1-n-butoxyethylperoxy)ethyl]propenoate (EBEPEP) was used in the free radical polymerization of methyl methacrylate (MMA), styrene (St), and butyl acrylate (BA) to produce end-functional polymers by a radical addition-substitution-fragmentation mechanism. The chain transfer constants (C(tr)) for EBEPEP in the three monomers polymerization at 60-degrees-C were determined from measurements of the degrees of polymerization. The C(tr) were determined to be 0.086, 0.91, and 0.63 in MMA, St, and BA, respectively. EBEPEP behaves nearly as an ''azeotropic'' transfer agent for styrene at 60-degrees-C. The activation energy, E(atr), for the chain transfer reaction of EBEPEP with PMMA radicals was determined to be 29.5 kJ/mol. Thermal stability of peroxyketal EBEPEP in the polymerization medium was estimated from the DSC measurements of the activation energy, E(ath) = 133.5 kJ/mol, and the rate constants k(th), of the thermolysis to various temperature. (C) 1994 John Wiley & Sons, Inc.