Abstract: The present invention provides a process for the free radical polymerization of one or more ethylenically unsaturated monomers, said process comprising polymerizing one or more ethylenically unsaturated monomers in the presence of one or more N-oxyl radicals of formula II, wherein X is S, NR5, O, SO or SO2, R5 is C1-C20-alkyl or C5-C8-cycloalkyl and R3 and R4 independently of one another, are C1-C4-alkyl, phenyl, naphthyl or an aromatic five-membered ring, or R3 and R4 together are —(CH2)o— and p and o, independently of one another, are an integer from 2 to 7.

Abstract: The invention provides a process for the living free radical addition polymerization of one or more ethylenically unsaturated monomers using at least one free-radical polymerization initiator and in the presence of one or more stable N-oxyl radicals, wherein at least one stable N-oxyl radical has polymerizable double bonds. The invention additionally provides polymers obtainable by this process, having a polydispersity index PDI of from 1.0 to 1.8, and provides for the use of stable N-oxyl radicals having polymerizable double bonds in the living free radical addition polymerization of one or more different ethylenically unsaturated monomers.