Novel multiresponsive microgels: synthesis and characterization studies

The dispersion polymerization of 2-(N-morpholino)ethyl methacrylate (MEMA) in the presence of ethylene glycol dimethylacrylate (EGDMA) cross-linker and diblock copolymer stabilizer in n-hexane afforded sterically stabilized multiresponsive PMEMA microgels. By changing the reaction parameters, a wide range of particle sizes (120-720 nm) was obtained. Both dynamic light scattering and electron microscopy studies confirmed monodisperse spherical morphologies. These microgels had a response to the solution pH, temperature, and ionic strength. As expected, PMEMA microgels acquired cationic character at low pH because of the protonation of all morpholino groups. Although PMEMA microgels are in a swollen state in both acidic media and at low temperatures, they are in a deswollen state in basic media at high temperatures and in the presence of electrolytes above pH 6. In addition to these multiresponsive behaviors, PMEMA microgels have the ability to swell in various organic solvents. They also interact very well with magnetic particles and gain responsiveness to the magnetic field. Multiresponsive behaviors of PMEMA microgels were investigated by using DLS, UV-vis spectrophotometry, and zeta potentiometry.