Preparation and characterization of pH-sensitive microgels of poly((2-dimethylamino) ethyl methacrylate)

pH-sensitive microgels of poly((2-dimethylamino) ethyl methacrylate) (PDMAEMA) were prepared by dispersion polymerization of 2-dimethylamino ethyl methacrylate in a mixed solvent of water/ethanol. (HNMR)-H-1, FTIR and SEM were used to confirm the chemical structure and morphological properties of the resulting microgels. Dynamic Light Scattering (DLS) was used to measure the hydrodynamic diameter of the particles. SEM micrographs showed that the microgel particles have a diameter of about 100-200 nm in dry state. Mean hydrodynamic diameter of the particles at their collapsed state at pH = 9.5 was found to be about 150 nm. DLS measurements at various pH values showed that the prepared microgels have a volume phase transition around pH = 8 at which the hydrodynamic diameter decreased from about 470 nm to around 150 nm corresponding to a 32 fold change in the mean volume of a microgel particle.