Surface characterization of solid solution/dispersion coatings

The phase behavior of model systems of drug mixed with two polymers of different chemical and physical properties was examined. The partitioning of drug between polymers and any excess solid drug phases was identified by the confocal Raman technique. It was shown that the variation of chemical properties of model drugs changes interactions with the polymers and thus changes the state of the drug at the surface and within the bulk of the coating. The coating cloudiness and any drug crystallization were revealed by optical microscopy. The overall coating thickness and the distribution of drug within the coating at 0.5 μm resolution were maped by the state-of-the-art scanning confocal Raman microscopy.