Investigation of the felodipine glassy state by atomic force microscopy

The glassy state of Felodipine was prepared by melting crystals of felodipi ne on a clean glass slide and cooling to room temperature. It has been conf irmed that glassy felodipine is a metastable state, and undergoes transform ation to the more stable crystalline form. Crystallization occurred slowly and spontaneously at room temperature, below the glassy state transition te mperature (T-g). The contact mode of atomic force microscopy was used for t opographical imaging of the glassy and crystalline states of felodipine. Wh en the glassy felodipine region next to the recrystallized zone was exposed to controlled mechanical stress through the tip, rapid additional crystall ization was observed. This crystallization process can be induced and image d in real time by atomic force microscopy. (C) 2001 Elsevier Science B.V. A ll rights reserved.