A small-angle neutron scattering study of the ethyl (n-octyl) phosphate micelles in water |
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Authors: | H Hirata S Katayama H Okabayashi M Furusaka T Kawakatsu |
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Institution: | (1) Present address: Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, 466 Nagoya, Japan;(2) National Laboratory for High Energy Physics, BSF, 1-1 Oho, 305 Tsukuba-shi Ibaraki, Japan;(3) Department of Physics, Tokyo Metropolitan University, Hachioji, 192-03 Tokyo, Japan |
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Abstract: | Summary Mixed-double chain anionic surfactants, barium- and lithium-salts of ethyl(n-octyl) phosphate (EOP), which are asymmetric in the molecular shape, and a series of identical chain di-n-alkyl phosphate lithium salts have been synthezized. The limiting partial molar volume of a PO
4
–
group (23.43±0.41 cm3 mol–1) for use in small-angle neutron scattering analysis was determined by density measurements of a series of identical chain di-n-alkyl phosphate lithium salts. For lithium EOP-D2O system, a critical micellar concentration (2.3 wt%) was determined by31P NMR spectra. The micellar shape and size in the EOP-water binary system has been investigated by using small-angle neutron scattering (SANS) spectra. It has been found that the micelles of barium EOP in water have the shape of a prolate spheroid and aggregation numbers (n) equal to 48 at 23°C and 52 at 50°C. For the lithium EOP-micellar system, it has been found that the minimum micelle with an aggregation numbern=21 is spherical and micellar growth and variation from the spherical to the prolate shape might occur with an increase in concen tration above the CMC. |
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Keywords: | Ethyl(n-octyl) phosphatemicelle SANS |
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