Solid state amorphization and glass transition of tri-O-methyl-β-cyclodextrin

TLDR: Amorphous solid of tri-O-methyl-β-cyclodextrin was formed by grinding the crystalline sample with a vibrating mill at room temperature as discussed by the authors.

Abstract: Amorphous solid of tri-O-methyl-β-cyclodextrin was formed by grinding the crystalline sample with a vibrating mill at room temperature. The amorphising process was examined by X-ray powder diffraction technique and differential scanning calorimetry (DSC). The Bragg peaks disappeared and the enthalpy of crystallization became constant for the sample ground for 25 min, indicating the apparent completion of the amorphization. A glass transition of the ground amorphous solid was found by DSC. The glass transition temperature Tg moved from 58°C to 79°C with grinding. The saturated Tg of the ground sample was the same as that of the liquid-quenched glass. No significant difference between the ground and liquid-quenched amorphous solids was found in the X-ray diffraction patterns. Infrared spectra of both amorphous solids, however, showed a definite difference for the band at 1194 cm−1 assigned to the rocking of the CH3 groups which are located at the molecular periphery.