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]pr openoate (EBEPEP) was used in the free radical polymerization of methy l methacrylate (MMA), styrene (St), and butyl acrylate (BA) to produce end-functional polymers by a radical addition-substitution-fragmentat ion mechanism. The chain transfer constants (C(tr)) for EBEPEP in the three monomers polymerization at 60-degrees-C were determined from mea surements 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 b ehaves nearly as an ''azeotropic'' transfer agent for styrene at 60-de grees-C. The activation energy, E(atr), for the chain transfer reactio n of EBEPEP with PMMA radicals was determined to be 29.5 kJ/mol. Therm al stability of peroxyketal EBEPEP in the polymerization medium was es timated from the DSC measurements of the activation energy, E(ath) = 1 33.5 kJ/mol, and the rate constants k(th), of the thermolysis to vario us temperature. (C) 1994 John Wiley & Sons, Inc.