The invention relates to the use of a co-polymer (A), which may be produced by means of radical polymerisation of a) at least one olefinic unsaturated monomer and b) at least one olefinic unsaturated monomer, different from olefinic unsaturated monomer (a), of general formula (I) R R C=CR R (I), where the groups R , R , R and R independently = H, substituted or unsubstituted alkyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl, cycloalkylaryl, arylalkyl or arylcycloalkyl, with the proviso that at least two of the variables R , R , R and R = substituted or unsubstituted aryl, arylalkyl or arylcycloalkyl, in particular substituted or unsubstituted aryl, in an aqueous or organic medium, for the production of functional organic powders, in particular fillers for coating materials, adhesives and sealing masses of all types.