78EUDRAGIT RS100 PLACEBO MICROSPHERES IN DIFFERENT MEDIA (2) STUDYING THE PHYSICO-CHEMICAL STRUCTURE OF MICROSPHRES AND THE EFFECT OF THE AQUEOUS PHASE ON THE MICROSPHERE MORPHOLOGYIt was tried to elucidate the role of the antiaggregating agents and the aqueous phases used on the morphology of the microsphere products prepared by solvent evaporation technique. Instrumental analysis like IR, Powder X -ray diffraction and DSC indicated that there is no residue of the antiaggregating agents used in all products prepared in different media in whic h the microspheres could be formed or not. Increase the PVP concentration over 1.5% led formation of polymer network structure in the aqueous phase which hampered the microspheres formation and increase the polymer fragments but could not protect the coacervation effect of chloride ions of 0.1N HCl for Eudragit RS100. At the same time the using of gelatin as an antiaggregating agent in 0.1N HCl led to protect the coacervation effect of the chloride ions of the medium for Eudragit RS10 0 as a result of capturing effect of the chloride ions by its positive charge acquire from its solubility in the acidic medium. In the other side it was found that, the effect of using of gelatin as an antiaggregating agent on the morphology of the products prepared in the other aqueous media, depends on gelatin concentration used. In addition the flow of all aqueous media used containing either PVP or gelatin as an antiaggregating agent at different concentrations was Newtonian and had no elasticity except phosphate buffer pH 7.4 containing PVP which led to the formation of compressed round flat shapes as a result of its rolling effect on the emulsified microspheres.omer.mady@gmx.atResearch512015Eudragit RS100,Aqueous phase,Rheology,Viscosity,Surface tensionMady O,Korsatko W,Ribitisch VRibitisch V,Institute für Pharmazeutische Chemie, Karl Franzens, Universität, Graz, Austria,Institute für Physikalische Chemie, Karl Franzens, Universität, Graz, Austria