Preparation and characterization of novel cationic pH-responsive poly(N,N'-dimethylamino ethyl methacrylate) microgels.

Novel monodisperse cationic pH-responsive microgels were successfully prepared by dispersion polymerization in ethanol/water mixture using N,N'-dimethylamino ethyl methacrylate (DMAEMA) as the monomer, poly(vinyl pyrrolidone) (PVP) as the steric stabilizer and N,N'-methylenebisacrylamide (MBA) as the cross-linker. The effects of various polymerization parameters, such as medium polarity, concentration of cross-linker, concentration of monomer, and concentration and molecular weight of stabilizer on the final diameter and monodispersity of poly(N,N'-dimethylamino ethyl methacrylate) (PDMAEMA) microgels were systematically studied. The pH-responsive characteristics of PDMAEMA microgels were also investigated. The experimental results showed that these microgels exhibited excellent pH-responsivity and significantly swelled at low pH values. The maximum ratio of volume change of the prepared microgels in response to pH variation was more than 11 times. It was found that the prepared microgels completely aggregated at the isoelectric point (IEP) around pH 6. On the other hand, the microgels were stable in aqueous solution at both low and high pH values. The results can be used for effectively controlled separation of particles.