Polycarboxylic acids and their salts corresponding to the following general formula[X]--(NHOC--Y--COO M).sub.n (I)in whichX is the residue of a hydrophobic, linear or branched vinyl oligomer having an average molecular weight M.sub.n of from 200 to 5000 and preferably from 300 to 3000,Y is the 1,2-vinylene, 1,2-ethylene, 1,3-propylene, 1,2-phenylene, 1,2-cyclohexen-4-ylene or 1,2-cyclohexylene group,n is a number of from 1.4 to 3.0 and preferably from 1.6 to 2.3 andM is hydrogen, an alkali metal, an ammonium, C.sub.1 -C.sub.4 alkylammonium or C.sub.2 -C.sub.3 hydroxyalkylammonium group, which are useful as surfactants and emulsifiers in aqueous systems.