A series of pH-responsive cationic microgels have been synthesized via semi-batch emulsion polymerization with 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) and ethyl acrylate (EA) as comonomers, and ethylene glycol dimethacrylate (EGDMA) as cross-linker. The effects of various conditions on the emulsion polymerization and the stability of microgels were studied in detail. The resultant microgels were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and rheometry. The pH-responsive behavior of the microgels was investigated by the measurements of Z-average diameter, zeta potentials, and the solution transmittance of the microgels at different pH values. Furthermore, the influence of NaCl solution on the stability of the microgels in aqueous solution was also studied. All the results show that the cationic microgels possess well pH-responsive property, and the phase variation happens at pH＝7. Furthermore, the addition of NaCl solution can influence the stability of the microgels and the critical flocculent concentration is about 1.3 mol•L－1.

Key words: emulsion polymerization, cationic microgel, pH-responsive, DMAEMA