A reaction product (A) which can be prepared by reaction, under free radical conditions, of at least one monomer (a) capable of free radical reaction, in the presence of at least one free radical initiator and of a radical of the formula (III) 1 where R1 to R3, in each case independently of one another, are hydrogen, methyl or a radical-stabilizing and/or bulky group selected from an unsubstituted or substituted, linear or branched alkyl of two or more carbon atoms, cycloalkyl, alcohol, ether, polyether, amine, aralkyl radical, a substituted or unsubstituted aromatic, heterocyclic or olefinic hydrocarbon, a halogen atom, a substituted or unsubstituted, linear or branched alkenyl or alkynyl group, nullC(O)R5, nullC(O)OR5, nullCR5R6nullOnullR7, nullOnullC(O)R5, nullCN, nullOnullCN, nullSnullCN, nullOnullCnullNR5, nullSnullCnullNR5, nullOnullCR5R6nullCR7R8NR9R10, nullNnullCnullO, nullCnullNR5, nullCR5R6-Hal, nullC(S)R5, nullCR5R6nullP(O)R7R8, nullCR5R6nullPR7R8, nullCR5R6nullNR7R8, nullCR5R6(OR7)(OR8), nullCR5R6(OR7)(NR8), nullCR5R6(NR7)(NR8), an anhydride, acetal or ketal group, nullSO2R5, an amidine group, nullNR5C(S)NR6, nullNR5C(S)nullOR6, nullNnullCnullS, nullNO2, nullCnullNnullOH, nullN(R5)nullNR6, nullPR5R6R7, nullOSiR5R6R7 or nullSiR5R6R7, where R5 to R10, independently of one another in each case, are defined in the same way as R1 to R5, or two of the radicals R1 to R4 form a C4- to C7-ring which in turn may be substituted or unsubstituted and, if required, may contain one or more heteroatoms, with the proviso that at least two of the radicals R1 to R3 are a radical-stabilizing and/or bulky group as defined above, has various uses.