New regulator compounds for a novel polymerization process for vinyl monomers, which yields polymers with improved control over composition and nearly full to full conservation of architectural integrity up to high conversion. The regulator compounds are defined by according to anyone of the Formulas 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H and 1I: wherein R1 stands for an optionally substituted secondary or tertiary alkyl or secondary or tertiary aralkyl; Z1 stands for —CN or a carboxylic acid ester of formula C(O)OR21; Z2 may be chosen from the group of —CN, carboxylic acid, salts of carboxylic acids, carboxylic acid ester, carboxylic acid amides, (hetero)aryl, alkenyl and halogen; R2, R3, R4 and R5 are each independently chosen from the group of H, alkyl, aralkyl, (hetero)aryl, —CN and carboxylic acid ester of formula C(O)OR22; R7 stands for a primary alkyl or primary aralkyl, —CN or hydrogen; Y stands for a bridging group and n is 2, 3, 4, 5 or 6; in case R1 stands for tertiary alkyl or tertiary aralkyl, R6 stands for a primary alkyl or primary aralkyl, —CN or a carboxylic acid ester of formula C(O)OR26; in case R1 stands for a secondary alkyl or secondary aralkyl, R6 stands for a primary or secondary alkyl or primary or secondary aralkyl, —CN, a carboxylic acid ester of formula C(O)OR26 or a phosphonic acid ester of formula P(O)(OR27)2, a (hetero)aryl or an alkenyl; R21, R22, R26 and R27 each independently stand for alkyl or aralkyl having from 1-30 carbon atoms, optionally containing heteroatoms.