Co-oligomers and copolymers having dispersant activity and usable as emulsifiers are based on esters of (meth)acrylic acid; where the co-oligomers and copolymers are comprised of the following components: (A) 60-95 wt. % of at least one (meth)acrylic acid ester of formula I ##STR1## where R represents hydrogen or methyl, and R.sub.1 represents a (possibly branched) alkyl group or a cycloalkyl group with 4-32 carbon atoms in the alkyl group; and (B) 5-40 wt. % of a (meth)acrylic acid ester of formula II ##STR2## where R' represents hydrogen or methyl, R.sub.2 represents an alkyl or aryl group with 1-50 carbon atoms, where R.sub.2 itself may be substituted with nitrogen or sulfur, n may be a number from 5 to 100, and m may be a number from 0 to 100; and, in the amount of 0-90 mol % of the monomer(s) of formula II, a hydroxyalkyl ester of (meth)acrylic acid, of formula III: ##STR3## where R" represents hydrogen or methyl, and R.sub.3 represents an alkyl group substituted with at least one hydroxyl group and having 2-30 carbon atoms; with the proviso that (A) and (B) together make 100 wt. %; and (C) an additional 0-75 wt. %, based on the weight of (A)+(B), of at least one 1-alkene having 4-42 carbon atoms.