Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 41: Glasses and Glass Transition II (jointly with DY, DF)
CPP 41.5: Vortrag
Donnerstag, 17. März 2011, 12:00–12:15, ZEU 114
(contribution withdrawn) Crystallization and induced glass transition of n-alcohols in silicon-nanochannels — •Rolf Pelster, Rene Berwanger, Carsten Biehl, and Christoph Schuhmacher — FR 7.2 Experimentalphysik, Universität des Saarlandes, D-66123 Saarbrücken, Germany
We have investigated the molecular dynamics of n-alcohols (C4H9OH - C11H23OH) confined in mesoporous silicon and silicon oxide with pore radii ranging from 3.5 to 7 nm. Using dielectric and infrared spectroscopy we show that 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:
Long-chain alcohols exhibit a crystalline structure at low temperatures. The confinement induces a lowering of the freezing temperature. The shorter the chain length or the smaller the pore radius, the lower the freezing temperature. Below the phase transition only the dynamics of amorphous wall layers are observable [1].
Short-chain alcohols behave differently. While bulk alcohols still freeze upon slow cooling, we observe a glass transition for the confined phase. The glass transition temperature is close to that reported for quenched bulk alcohols. We thus conclude that nano-confinement suppresses the crystallization process and induces a glass transition.
[1] R. Berwanger, Ch. Schumacher, P. Huber, and R. Pelster, Eur. Phys. J. Special Topics 189, 239-249 (2010)