The invention relates to a method for producing aqueous dispersions of (co)polymers using a polymer with cationic functionality, optionally with the addition of the usual additives. The polymer with cationic functionality is obtained by (co)polymerising olefinically unsaturated (co)monomers in an aqueous medium, at least one of said (co)monomers having a cationic functionality. Other (co)monomers are added and the polymerisation is carried out in the presence of suitable initiators. The polymers and/or (co)monomers are chosen and the method is controlled in such a way that a (co)polymer particle is formed with heterogeneous morphology and the resulting dispersed (co)polymer has a glass transition temperature Tg of more than approximately 50 DEG C. The invention also relates to a method for forming the polymer with cationic functionality in the presence of a seed in situ, and to redispersible powders and their use.