Browsing by Author "Tiddy, Gordon J. T."

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Nuclear magnetic resonance technique to distinguish between micelle size changes and secondary aggregation in anionic and nonionic surfactant solutions
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Staples, Edwin J.; Tiddy, Gordon J. T.
The presence of surfactants in large micelles gives rise to broad n.m.r. resonances because of the long correlation time for diffusion around the micelle. This has been used to investigate the structure of surfactant aggregates in systems where other evidence indicates that large micelles occur. For polyethylene oxide surfactants at the cloud point, the surfactant micelles are small and the large units are formed by secondary aggregation of small micelles. For sodium dodecylsulphate with added salt, octanol or other surfactants, large micelles are formed. The changes in micelle size indicated by changes in n.m.r. linewidths are in agreement with changes measured by the quasi-elastic light scattering technique.
Phase Structure and Rheological Properties of a Mixed Zwitterionic/Anionic Surfactant System
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Saul, Dorothy; Tiddy, Gordon J. T.; Wheeler, Barbara A.; Wheeler, Phillip A.; Willis, Edwin
The phase diagram of the mixed zwitterionic/anionic surfactant system hexadecyldimethyl- ammoniopropancsulphonate/sodium dodecyl sulphate/water has been determined in the aqueous region (>90.0 % water) by optical microscopy and low angle X-ray scattering; the phases observed were an isotropic surfactant solution and a hexagonal liquid crystalline phase. Some aqueous solutions were found to be viscoelastic and the composition boundaries of solutions with these properties were parallel to the phase boundaries. N.m.r. was used additionally to study the structure of the viscoelastic solutions and the results are interpreted using a model which involves the existence of both normal spherical micelles and cylindrical micelles in equilibrium.
Phase Structure, Nuclear Magnetic Resonance and Rheological Properties of Viscoelastic Sodium Dodecyl Sulphate and Trimethylammonium Bromide Mixtures
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Barker, Christopher A.; Saul, Dorothy; Tiddy, Gordon J. T.; Wheeler, Barbara A.; Willis, Edwin
The phase diagram of octyltrimethylammonium bromide and sodium dodecyl sulphate (SDS) in water (>90 %) is reported at 298 K; the phase regions observed are liquid, two liquid, and liquid plus liquid crystal. Liquids with viscoelastic properties occur close to the SDS rich liquid boundary, and a correlation is observed between the surfactant n.m.r. linewidths and the rheological properties of these liquids. The most likely explanation of these effects is one involving the occurrence of both cylindrical and spherical micelles, but the possibility that the viscoelasticity is due to the presence of a microemulsion can not be excluded.
Sodium-23 quadrupole splittings in lyotropic liquid crystals. Relationship to electrical double layer theory and estimates of double layer dimensions
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (05), 1978) Tiddy, Gordon J. T.; Lindblom, Göran; Lindman, Björn
It is proposed that the magnitudes of n.m.r. quadrupole splittings of ions in lyotropic liquid crystals are related to the fractional concentration of the ions in the bound water at the lipid/water interface. Ions in the remaining water have zero splittings. Sodium-23 splittings are reported for cationic and anionic amphiphile systems at different salt concentrations and strongly support the proposed explanation. In favourable cases it is possible to obtain measurements of the double layer thickness. It was not possible to observe any displacement of sodium ions by magnesium or lanthanum ions in the concentration ranges studied.