Physical vapor deposition of indomethacin (IMC) was used to prepare glasses with unusual thermodynamic and kinetic stability. By varying the substrate temperature during the deposition from to the glass transition temperature , it was determined that depositions near resulted in the most stable IMC glasses regardless of substrate. Differential scanning calorimetry of samples deposited at indicated that the enthalpy was less than the ordinary glass prepared by cooling the liquid, corresponding to a reduction in the fictive temperature. Deposition at also resulted in the greatest kinetic stability, as indicated by the highest onset temperature. The most stable vapor-deposited IMC glasses had thermodynamic stabilities equivalent to ordinary glasses aged at for . We attribute the creation of stable IMC glasses via vapor deposition to enhanced surface mobility. At substrate temperatures near , this mobility is diminished or absent, resulting in low stability, vapor-deposited glasses.
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More precisely, indicates the temperature at which the extrapolated enthalpy lines of the liquid and glass intersect, as shown in Fig. 1.
