Superstructure phase in the binary C₂₈H₅₈:C ₃₆H/D₇₄ system

Blends of the normal alkane C₂₈H₅₈ with either protonated or deuterated C₃₆ alkane, xC₂₈H₅₈.(1 - x)C₃₆H/D₇₄, have been rapidly cooled from the melt and aged under ambient conditions for at least seven months. For compositions 0.94 ≥ x ≥ 0.65, both Bragg peaks and associated satellite peaks appear in the small-angle X-ray scattering. The Bragg peaks may be indexed to multiple order reflections from the average spacing of the chain lengths of the two components. The offset in q between these peaks is constant for each composition, but dependent on molar composition, and indicates that a superstructure phase forms on prolonged annealing. This new phase appears to be a solid solution and is found for both the protonated and deuterated samples, with a larger cell in the former system. For the remaining compositions, additional peaks indicate formation of a C₃₆-rich phase.