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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 35: Poster: Glasses and Glass Transition
CPP 35.1: Poster
Wednesday, March 24, 2010, 17:30–19:00, Poster B2
Glass Transition and Crystallization of n-Alcohols Confined in Silicon Nano-Channels — •René Berwanger, Christoph Schumacher, and Rolf Pelster — FR 7.2 - Experimentalphysik, Universität des Saarlandes, D-66123 Saarbrücken, Germany
We present the investigation of several n-alcohols (C4H9OH-C16H33OH) in mesoporous silicon and silicon oxide by infrared and dielectric spectroscopy. The temperature of the liquid-solid phase transition and the structure of the solid phase depend on both the chain length and the radius of the pores (r = 3 nm-7 nm).
Long-chain alcohols exhibit a crystalline structure at low temperatures. In confinement this is an orthorhombic β-form, where the molecule axes are perpendicular to the pore axis, while in the bulk state a poly-crystalline structure of orthorhombic β- and monoclinic γ-form is observed1. In addition, confinement yields to a lowering of the transition temperatures of the liquid → Rotator-(II)-phase (RII) and RII→ crystalline phase. On the other hand, short-chain alcohols in narrow pores (r ≈ 3nm) form a glassy state at low temperatures, but crystallize in larger pores.
1 R. Berwanger, A. Henschel, P. Huber, K. Knorr, R. Pelster, Phys. Rev. B, 79, 125442 (2009)