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) ##STR1##

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, —C(O)R₅, —C(O)OR₅, —CR₅R₆—O—R₇, —O—C(O)R₅, —CN, —O—CN, —S—CN, —O—CNR₅, —S—CNR₅, —O—CR₅R₆—CR₇R₈NR₉R₁₀, —NCO, —CNR₅, —CR₅R₆-Hal, —C(S)R₅, —CR₅R₆—P(O)R₇R₈, —CR₅R₆—PR₇R₈, —CR₅R₆—NR₇R₈, —CR₅R₆(OR₇)(OR₈), —CR₅R₆(OR₇)(NR₈), —CR₅R₆(NR₇)(NR₈), an anhydride, acetal or ketal group, —SO₂R₅, an amidine group, —NR₅C(S)NR₆, —NR₅C(S)—OR₆, —NCS, —NO₂, —CN—OH, —N(R₅)NR₆, —PR₅R₆R₇, —OSiR₅R₆R₇ or —SiR₅R₆R₇, where R₅ to R₁₀, independently of one another in each case, are defined in the same way as R₁ to R₄, 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.