Monomers of 4-vinylaniline, and 4-vinylpyridine were studied to investigate the influence of charges of the initiator on the dispersion stability of the new polymer particles created using soap-free emulsion polymerization. The surface of the polymer particles included some functional groups originated from the monomers and some from the initiators, based on measurement of their zeta potentials. Therefore, during the polymerization, the dispersion stability was maintained when using cationic initiators. On the other hand, aggregation of particles occurred when anionic initiators were used due to the electrostatic attraction between the hydrophilic and hydrophobic groups on the polymer surfaces.