Phase Separation in the Organic Solid State: The Influence of Quenching Protocol in 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 mismatch, molar composition, isotopic substitution and confinement. 2:1 C₂₈H₅₈:C₃₆D₇₄ mixtures have been investigated after subjection to a cooling rate varying over three orders of magnitude and intermediate annealing prior to reaching ambient. Quenching at 100°C/min yields similar behaviour to intermediate annealing between the pure components' melting points. Slow cooling at 0.1°C/min generates significantly greater ordering and behaviour comparable to that obtained from annealing mid-way between the mixing transition and the C₂₈H₅₈ melting point.

Keywords:

• DSC
• lamellar structures
• n-alkane blends
• SANS
• SAXS

Acknowledgments

Support by Access to Major Research Facilities is gratefully acknowledged. This work has benefited from the use of the Intense Pulsed Neutron Source at Argonne National Laboratory which is funded by the U.S. Department of Energy, BES-Materials Science, under Contract W-31-109-ENG-38. We would also like to thank the staff at the SRS and Professor Charles Han at the Institute of Chemistry, Chinese Academy of Sciences who first suggested this experiment.