4. Glass transition of amorphous multicomponent systems

Drugs formulated in the amorphous state, and their use, often involve a homogeneous amorphous mixture of several components. Determining the glass transition temperature of an amorphous multi-component system provides important information about the physical behavior of this system. For example, T _g , identified by a specific heat jump in DSC, is an indicator of the molecular mobility of an amorphous system, and is therefore an important datum for assessing the system's physical stability.

If an amorphous mixture of several components exhibits a single glass transition, this indicates that the mixture is homogeneous at the molecular level. The T _g value of the mixture is generally between the T _g values of the individual components....