Phase separation in the organic solid state: simultaneous synchrotron SAXS / DSC studies of unstable n-alkane blends

Abstract

Blends of normal alkanes form lamellar structures, when quenched from the melt, in which the separation of the individual chains may be controlled by the chain-length difference, molar composition, isotopic substitution and confinement. We have performed simultaneous synchrotron small-angle X-ray scattering and differential scanning calorimetry studies on 2:1 C28H58:C36D74 mixtures as a function of cooling protocol. Their simultaneous collection enables the temperature-dependent nanostructural changes to be correlated with phase transitions. The data are further complemented by small-angle neutron scattering highlighting the separation of the individual chains via isotopic contrast and optical microscopy indicating changes occurring on the macroscopic scale.