PARTICLE SIZE AND MONODISPERSITY OF THERMO-RESPONSIVE POLY(N-ISOPROPYLACRYLAMIDE)HYDROGEL MICROSPHERES
Thermo-responsive poly(N-isopropylacrylamide-co-styrene)[P(NIPAM-co-St)] hydrogel microspheres were prepared by surfactant-free emulsion polymerization. The effects of initiator dosage, stirring rate, phase ratio and polymerization time on particle size and monodispersity were investigated.The results showed that, with increasing initiator dosage,mean diameter increased slightly to a maximum, and then decreased drastically; meanwhile, the monodispersity of the particles became a little better at first, and then became worse significantly. With increasing stirring rate,particle diameter decreased while the monodispersity became worse. When the amount of phase rate increased, the mean diameter became larger simply, whereas the monodispersity became worse firstly and then became better again. As the polymerization proceeded, the mean diameter of the particles hardly changed, and the monodispersity became better gradually. The microspheres prepared under the optimum experimental conditions showed satisfactory particle size and monodispersity.