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Freezing/Melting Transition of Physically Restricted n-Decane

Published online by Cambridge University Press:  15 February 2011

P. M. Hoffmann  and
V. M. Malhotra
P. M. Hoffmann
Affiliation:
Current Address: Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218
V. M. Malhotra
Affiliation:
Department of Physics, Southern Illinois University at Carbondale, Carbondale, Illinois 62901
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Abstract

We undertook differential scanning calorimetry (DSC) measurements at 170 K < T < 300 K on n-decane, physically confined in 8 nm (= diameter D) porous silica derivatized with various functional groups, to understand how surface structure of the confining media affects the freezing or melting transition of the n-decane. Though we observed a typical depression (ΔT) in the freezing or melting transition temperature of the physically confined decane, our results failed to manifest usual linear dependence of ΔT on D−1 when the expected contraction in D, due to the presence of aminopropyl-, hexyl-, phenyl- or trimethyl-groups on the silica surface, was taken into account. However, it is worth noting that a linear behavior was observed between ΔT and D−1 if only alkane-chain derivatized hosts were considered. Our results also indicate that a large fraction of physically confined n-decane (35 to 70 %), depending on the host silica, does not participate either in the melting or freezing transition. The most interesting behavior observed in the present study is the occurrence of the unusual two peaks associated with the freezing transition of physically confined decane. This bimodal behavior is strongly dependent on the chemistry of the confining silica host's surface.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 366: Symposium N – Dynamics in Small Confining Systems , 1994 , 295
Copyright
Copyright © Materials Research Society 1995

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