Revealing the pure confinement effect in glass-forming liquids by dynamic mechanical analysis

Koppensteiner, J. and Schranz, W. and Carpenter, M. A. (2010) Revealing the pure confinement effect in glass-forming liquids by dynamic mechanical analysis. Physical Review B (Condensed Matter and Materials Physics), 81 (2). 024202. DOI

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The dynamic mechanical response of mesoporous silica with coated inner surfaces confining the glassforming liquid salol is measured as a function of temperature and frequency 1–100 Hz for various pore sizes 2.4–7.3 nm. Compared to former results on natural pores, a distinct acceleration of dynamics due to the removal of surface-related retardation of molecular dynamics is found now, which can be fitted by a homogeneous relaxation using an unmodified Vogel-Fulcher-Tammann relation. This lubrication effect leads to a stronger decrease in the glass transition temperature Tg with decreasing pore size. The present data allow to quantify and separate competing side effects as surface bondings and negative pressure from the pure confinement induced acceleration of molecular dynamics with decreasing pore size. We analyze the dynamic elastic susceptibility data in terms of a recently proposed procedure C. Dalle-Ferrier et al., Phys. Rev. E 76, 041510 2007, which relates the number Ncorr,T of molecules, whose dynamics is correlated with a local enthalpy fluctuation, to the three-point dynamic susceptibility T. The observed increase of Ncorr,T with decreasing temperature strongly indicates that the size of dynamic heterogeneities increases when approaching the glass transition.

Item Type: Article
Uncontrolled Keywords: 2010AREP; IA61;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Physical Review B (Condensed Matter and Materials Physics)
Volume: 81
Page Range: 024202
Identification Number:
Depositing User: Sarah Humbert
Date Deposited: 03 Sep 2010 15:27
Last Modified: 23 Jul 2013 10:00

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