Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Polymer Physics III: Interfaces

CPP 12.6: Talk

Tuesday, March 27, 2007, 11:30–11:45, H40

Preferred orientations and stability of medium length n-alkanes solidified in mesoporous silicon — •Anke Henschel, Tommy Hofmann, Patrick Huber, and Klaus Knorr — Saarland University, Saarbruecken, Germany

The n-alkanes C₁₇H₃₆, C₁₉H₄₀, and C₂₅H₅₂ have been imbibed and solidified in mesoporous, crystalline silicon with a mean pore diameter of 10nm. The structures and phase sequences have been determined by x-ray diffractometry. Apart from a reduction and the hysteresis of the melting/freezing transition, we find a set of six discrete orientation states ("domains") of the confined alkane crystals with respect to the lattice of the silicon host. The growth process responsible for the domain selection is interpreted as a nano-version of the Bridgman technique known from single crystal growth. Oxidation of the pore walls leads to extrusion of the hydrocarbons upon crystallization, whereas the solidified n-alkanes investigated in non-oxidized, porous silicon are thermodynamically stable.