The present invention relates to a latex with modified surface chemistry, which may be obtained by carrying out a free-radical emulsion polymerization in the presence of at least one ethylenically unsaturated monomer or at least one polymer containing residual ethylenically unsaturated bonds,of at least one free-radical polymerization initiator,of at least one water-soluble and/or water-dispersible monoblock, diblock or triblock polymer comprising at its end an active group capable of forming a radical, chosen from dithioesters, xanthates, thioether-thiones and diothiocarbamates. The invention similarly relates to redispersible powders that may be obtained by drying the said latices.