Small-angle neutron scattering study of the structural effects of substitution of tetramethylammonium for sodium as the counterion in dodecyl sulfate micelles

Journal Article · Thu Nov 20 04:00:00 EST 1986 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100282a017· OSTI ID:7203792

Berr, S S; Coleman, M J; Jones, R R.M.; Johnson, Jr, J S

Small-angle neutron scattering (SANS) data have been obtained at 303 K for aqueous micellar solutions of CH/sub 3/(CH/sub 2/)/sub 11/SO/sub 4/Na (sodium dodecyl sulfate (SDS)) and CH/sub 3/(CH/sub 2/)/sub 11/SO/sub 4/N(CH/sub 3/)/sub 4/ (tetramethylammonium dodecyl sulfate (TMADS)) and their deuterated analogues CH/sub 3/(CH/sub 2/)/sub 10/CD/sub 2/SO/sub 4/Na (D/sub 2/-SDS) and CH/sub 3/(CH/sub 2/)/sub 11/SO/sub 4/N(CD/sub 3/)/sub 4/ (D/sub 12/-TMADS). Results have been obtained for 0.4 mol dm/sup -3/ surfactant in various H/sub 2/O/D/sub 2/O mixtures and for TMADS as a function of surfactant concentration in D/sub 2/O. The SANS data are well described by charged, monodisperse hard spheres interacting through a screened Coulomb potential. The asphericity and the polydispersity of the systems were estimated to be small. The deuterium for the deuterated surfactants lies mainly in the Stern region of the micelle and increases contrast between the hydrocarbon core and the water-saturated Stern layer. Therefore, these deuterated micellar systems were used to determine the radius of the dry core, which was then used in the determination of the structural parameters for the micellar systems. The degree of hydration was determined without resorting to the assignment of values for the water of hydration for the individual ions present. It was found that TMADS micelles are smaller and have a higher charge, smaller degree of aggregation, and less but more deeply penetrating water than do SDS micelles. Both SDS and TMADS micelles had substantial amounts of hydrocarbon residing in the aqueous Stern layer.

• Research Organization: Wake Forest Univ., Winston-Salem, NC
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 7203792
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 90:24; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
654003 -- Radiation & Shielding Physics-- Neutron Interactions with Matter
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALKALI METAL COMPOUNDS
ALKANES
AMMONIUM COMPOUNDS
BARYON REACTIONS
DATA
DEUTERIUM COMPOUNDS
DIMENSIONS
EXPERIMENTAL DATA
HADRON REACTIONS
HYDRATION
HYDROCARBONS
HYDROGEN COMPOUNDS
INFORMATION
MEDIUM TEMPERATURE
MICELLAR SYSTEMS
NEUTRON REACTIONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
SCATTERING
SMALL ANGLE SCATTERING
SODIUM COMPOUNDS
SOLVATION
STRUCTURAL CHEMICAL ANALYSIS
SULFATES
SULFUR COMPOUNDS