The structure of normal ionic micelles by interpretation of small-angle neutron scattering data from selectively labeled (/sup 2/H, /sup 19/F) surfactant solutions

Technical Report · Mon Dec 01 04:00:00 EST 1986

OSTI ID:6842688

Berr, S S

We have determined the structure of micelles formed in water by several classes of ionic surfactants under a variety of experimental conditions using small-angle neutron scattering (SANS) techniques. Contrast between the micelles and the solvent was achieved through either selective deuteration or fluorination of the surfactant, or through the use of D/sub 2/O. Interpretation of SANS data was facilitated by the use of Hayter, Penfold, and Hansen's rescaled Mean Spherical Approximation theory to calculate the scattering due to interparticle interactions. We have devised a number of micelle models, both spherical and ellipsoidal, to account for the scattering due to single micelles. It was found that changing the solvent from H/sub 2/O to D/sub 2/O results in the formation of larger micelles due to changes in the solvent-surfactant hydrocarbon interactions. This solvent isotope effect increased as the length of the alkyl chain increased. The fractional micellar charge did not change with respect to isotopic composition of solvent. We found that alkyltrimethylammonium bromide surfactants form drier micelles than do the sodium alkyl sulfate surfactants of equal chain length. Also, all micelles studied were found to be dry near the critical micelle concentration (cmc) and to become increasingly wetter as the concentration increased. The increase in aggregation number with respect to the square root of surfactant concentration was found to be linear for all systems studied. 80 figs.

• Research Organization: Wake Forest Univ., Winston-Salem, NC (USA). Dept. of Chemistry
• DOE Contract Number: AC05-76OR00033
• OSTI ID: 6842688
• Report Number(s): DOE/OR/00033-T409; ON: DE88015642
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400101* -- Activation
Nuclear Reaction
Radiometric & Radiochemical Procedures
COHERENT SCATTERING
DIFFRACTION
ENERGY
FORMATION FREE ENERGY
FREE ENERGY
HYDROCARBONS
IONIC COMPOSITION
MATHEMATICAL MODELS
MICELLAR SYSTEMS
MOLECULAR STRUCTURE
NEUTRON DIFFRACTION
NUCLEAR MODELS
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
SCATTERING
SHELL MODELS
SMALL ANGLE SCATTERING
SURFACTANTS
THERMODYNAMIC PROPERTIES