Both 2,2,6,6-tetramethyl-4-piperidiny-acrylate (ATMP) and -methacrylate (MTMP) are acrylic ester monomers which form stable N-oxyl free radicals rather easily.The binary and ternary copolymerizations of ATMP and MTMP with other monomers were studied.It was found that the relative reactivities of these monomers are in the descending order of St>MA>MTMP>ATMP>VAc.While the rela- tive reactivities of their corresponding radicals are in the ascending order of St·