Aqueous Glasses as Solid Solutions

It is now clear that, on a molecular scale, glasses must be treated as liquids, because they do not possess long-range structural order. Their observed quasi-solid properties originate from their extremely high 

Thermodynamically, a multicomponent glass can usually be treated as a homogeneous solid solution. It might then be expected that for chemically similar molecules the conventional mixing rules might apply, perhaps even be reflected in the Tg omposition relationship. This has indeed been found to be the case for binary PHC blends, where neither 

A selection of salts that form stable eutectics (E), unstable glasses (UG) or that remain amorphous (SG) during freezing 

As regards structural properties of PHC glasses that find applications in the formulation of drugs destined for freeze-drying, hard information is limited. By hard information we understand diffraction data from which atomic distances and molecular orientations in space can be calculated. While there is an abundance of X-ray diffraction data for crystalline PHCs, such techniques do not see hydrogen atom positions. No direct information about hydrogen bonds can therefore be obtained, except by speculation, based on observed 0-0 distances. 

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