Structures of Surfactant System Studied by Positron Annihilation Lifetime Spectroscopy
Surfactant system has many applications in industry. Many investigations have been carried out on surfactants using various methods such as small-angle neutron scattering (SANS), small-angle x-ray scattering(SAXS),conductivity freeze-fracture electron microscopy and nuclear magnetic resonance(NMR...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English English |
| Published: |
1996
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| Online Access: | http://psasir.upm.edu.my/id/eprint/8605/1/FSAS_1996_3_A.pdf http://psasir.upm.edu.my/id/eprint/8605/ |
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| Summary: | Surfactant system has many applications in industry. Many
investigations have been carried out on surfactants using various methods
such as small-angle neutron scattering (SANS), small-angle x-ray scattering(SAXS),conductivity freeze-fracture electron microscopy and nuclear
magnetic resonance(NMR).In the positron annihilation lifetime spectroscopy
technique, the lifetime ('t2)of positron that interacts with surfactant medium is
measured using fast coincidence system. The intensity of formation of
orthopositronium(12), when positron interact with aggregate of surfactant
system are sensitive to phase changes. In amphiphilic system with bicontinous character geometry of periodic phase can be explained using
minimal surfaces. Factors influencing the topology includes the length of
surfactant and cosurfactant tails and the aqueous volume fraction. Positron
are readily attracted to these centres. Changes in the geometry of the
interfacial layer thus will influence the lifetime and intensity of the
orthopositronium atom formed. These parameters are obtainable using the
POSITR ON FIT programme.
In this study, three surfactant systems were investigated. Firstly, the
intensity (12) and lifetime ("(2) of the Didodecyl DimethylAmmonium Bromide
(ODAB) - Water - Octane system were measured at various amount of water
content in the surfactant system in the diamond and body centred cubic
phases. A symmetry transitions from diamond phase to body-centred cubic
phase was observed in this system. |
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