Glassy crystalline state and water sorption of alkyl maltosides.

A differential scanning calorimetric and sorption calorimetric study of two alkyl maltosides, C8G2 and C10G2, was performed. In the dry state, C8G2 and C10G2 do not form solid crystals but undergo a glass transition upon temperature change. The glass is partly ordered and has the same lamellar structure as the liquid crystals formed by the two maltosides. To reflect the presence of the glass transition and the structure, the terms "glassy crystals" and "glassy liquid crystals" can be used. A mechanism of the relaxation of the glassy crystals based on the results of small-angle X-ray scattering experiments is proposed. Experiments on water sorption showed that the glassy crystals turn into lyotropic liquid crystals upon sorption of water at constant temperature. This isothermal glass transition can be characterized by water content and change of partial molar enthalpy of mixing of water. A method to calculate the phase diagram liquid crystals-glassy liquid crystals is proposed.