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Title: Surface Freezing in Binary Alkane-Alcohol Mixtures

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914237
Report Number(s):
BNL-78805-2007-JA
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. E; Journal Volume: 74
Country of Publication:
United States
Language:
English
Subject:
national synchrotron light source

Citation Formats

Ofer,E., Sloutskin, E., Tamam, L., Ocko, B., and Deutsch, M.. Surface Freezing in Binary Alkane-Alcohol Mixtures. United States: N. p., 2006. Web. doi:10.1103/PhysRevE.74.021602.
Ofer,E., Sloutskin, E., Tamam, L., Ocko, B., & Deutsch, M.. Surface Freezing in Binary Alkane-Alcohol Mixtures. United States. doi:10.1103/PhysRevE.74.021602.
Ofer,E., Sloutskin, E., Tamam, L., Ocko, B., and Deutsch, M.. Sun . "Surface Freezing in Binary Alkane-Alcohol Mixtures". United States. doi:10.1103/PhysRevE.74.021602.
@article{osti_914237,
title = {Surface Freezing in Binary Alkane-Alcohol Mixtures},
author = {Ofer,E. and Sloutskin, E. and Tamam, L. and Ocko, B. and Deutsch, M.},
abstractNote = {},
doi = {10.1103/PhysRevE.74.021602},
journal = {Phys. Rev. E},
number = ,
volume = 74,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • Surface freezing was detected and studied in mixtures of alcohol and alkane molecules, using surface tensiometry and surface-specific x-ray scattering methods. Considering that surface freezing in pure alkanes forms an ordered monolayer and in alcohols it forms an ordered bilayer, the length mismatch repulsion was minimized by varying the carbon number of the alkane component around 2n, where n is the carbon number of the alcohol molecule. A solutionlike behavior was found for all mixtures, where the ideal liquid mixture phase-separates upon freezing both in the bulk and the surface. The solid exhibits a herringbone crystalline phase below an alkanemore » mole fraction {phi}{sub t}{approx_equal}0.8 and a rotator phase above it. The surface frozen film below {phi}{sub t} is an alkane monolayer exhibiting a next-nearest neighbor molecular tilt of a composition-dependent magnitude. Above {phi}{sub t}, no diffraction peaks were observed. This could be explained by the intrinsically shorter-range order of the rotator phase and a possible proliferation of defects.« less
  • No abstract prepared.
  • No abstract prepared.
  • A previously derived association model for mixtures of any number of alcohols and alkanes is applied here to alcohol-alkane binary systems. The model contains two adjustable parameters: a self-association constant for the alcohol and a parameter that reflects physical interactions. Correlations for the two parameters are presented which allow the model to be used as a two-, one-, or zero-parameter model, depending on the amount of experimental data available. All three forms of the model provide adequate results for these systems over a fairly wide temperature range.
  • Surface freezing of a crystalline monolayer has been observed at the free surface of liquid binary mixtures of normal alkanes by x-ray and surface tension measurements. Two dramatically different behaviors are found for the monolayer properties depending on {Delta}{ital n}, the difference in the components` carbon numbers. For small {Delta}{ital n}, the variation with temperature and concentration is continuous. For large {Delta}{ital n}, the variation is discontinuous, exhibiting surface segregation and 2D structural phase transitions. A theory based on competition between entropic mixing and a repulsive interaction due to chain length mismatch accounts well for the observed phenomena.