Application of Broadband Dielectric Spectroscopy to Study Molecular Mobility in Pharmaceutical Systems

Broadband dielectric spectroscopy (BDS) is a very useful method for investigating the molecular dynamics of various materials because it enables monitoring the molecular mobility as reflected in the relaxation processes over a wide frequency range up to 16 decades. BDS finds application in many fields of science and technology, including investigations of pharmaceutical systems. Since amorphous drugs are usually thermodynamically unstable and may undergo recrystallization during the processing, storage, and use of the product, the main challenge in working with amorphous form of drugs is improving their physical stability as well as proper identification and understanding of the physical factors that govern crystallization from the glassy state. The dominant relaxation process in the supercooled liquid state observed at temperatures higher than the glass transition temperature is the structural α-relaxation. In the glassy state the a-relaxation process becomes very slow, and usually only secondary relaxations are observed in the dielectric spectra.