Effects of isotopic substitution on the critical behavior of aqueous solutions of n-dodecylhexaoxyethylene glycol monoether (C/sub 12/E/sub 6/)
The critical behavior of a nonionic surfactant, n-dodecylhexaoxyethylene glycol monoether (C/sub 12/ E/sub 6/) in D/sub 2/O, is examined using static and dynamic light scattering and small angle neutron scattering (SANS). Modification of the short-range attractive interactions responsible for phase separation by substitution of D/sub 2/O for H/sub 2/O has no effect on the measured universal critical exponents describing the divergence of the correlation length (..nu.. = 0.6 +- 0.05) and the isothermal compressibility (..gamma.. = 1.2 +- 0.1) although such substitution results in a reduction of both the nonuniversal amplitudes and critical temperatures. The measured exponents are the same as those of binary molecular fluids. However, in contrast to binary fluids, significant deviations from the Ornstein--Zernike form are observed at intermediate length scales in SANS measurements near the critical point. Isotopic substitution also preserves the dynamic scaling of the Kawasaki form for the measured Rayleigh linewidth, as found previously for H/sub 2/ O (Ref. 1). However, this scaling is restricted to a more limited range of distance from the critical point than the static scaling. A maximum in compressibility at the critical isochore is reflected in the concentration dependence of both the compressibility and diffusion coefficient even large distances (approx.25 /sup 0/C) from the coexistence curve. Estimates of micelle size, shape, and polydispersity are obtained.
- Research Organization:
- Division 1152, Sandia National Laboratory, Albuquerque, New Mexico 87105
- OSTI ID:
- 6566189
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 90:3; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
AQUEOUS SOLUTIONS
COHERENT SCATTERING
COMPRESSIBILITY
CRITICAL TEMPERATURE
DEUTERIUM
DIFFRACTION
DIFFUSION
DISPERSIONS
HEAVY WATER
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
LIGHT SCATTERING
MECHANICAL PROPERTIES
MICELLAR SYSTEMS
MIXTURES
NEUTRON DIFFRACTION
NUCLEI
ODD-ODD NUCLEI
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SCATTERING
SOLUTIONS
STABLE ISOTOPES
SURFACTANTS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
WATER