<p>NMR methods have been designed and employed in studying ofcomplex liquids and solids formed by surfactants. PGSE NMRexperiments are easily biased by convection; this artifact canbe avoided by changing the sample holder and by usingconvection-compensated pulse sequences. The temperaturedistribution within samples was controlled using thetemperature dependent order parameter for CBr<sub>2</sub>H<sub>2</sub>dissolved in a thermotropic nematic solvent.Electronic ringing that often spoils accurate NMR experimentsfor broad lines was removed by the using composite pulses andquadrupole echo sequences with appropriate phase cycles.</p><p>Field-dependent<sup>81</sup>Br and<sup>35</sup>Cl NMR relaxation studies in micellar solutions ofC<sub>16</sub>TAX surfactants showed that the structure ordynamics of the hydration shell is more influenced by thesurfactant cation for bromide than for chloride, in agreementwith their position in the Hoffmeister series. The presence ofa small but significant frequency-dependent relaxation showedthat the lateral self diffusion of the anions may be reduced ascompared to its bulk value in diluted solutions but only with afactor of 1.0 - 2.5. The ions are clearly not "bound" to thesurface. A field-dependent<sup>2</sup>H NMR relaxation study on the CTABr-α-<i>d</i><i>2</i>and benzene-<i>d</i><i>6</i>showed an initial one-dimensional micellargrowth followed by the appearance of microemulsion droplets onaddition of benzene. The local mobility of the benzene wasreduced when solubilized in small amounts, consistent with aninitial average location of benzene at the micellar interface.The surfactant diffusion coefficients fromconvection-compensated PGSE NMR experiments in the C<sub>12</sub>E<sub>8</sub>-D<sub>2</sub>O system showed monotonous growth of the micellesupon increasing temperature. Emulsion droplets in the C<sub>12</sub>E<sub>5</sub>-decane-D<sub>2</sub>O system where shown to coarsen according to theOstwald ripening theory after being brought out of equilibriumby a temperature drop. X-ray scattering and<sup>2</sup>H NMR line-shape and relaxation experimentssuggested that complex solids formed by a partly-sulfatedpolysaccharide and C<sub>n</sub>TAB exhibit regular ordering at both microscopicand mesoscopic length scales.</p><p><b>Keywords</b>: CTAB, CTAC, C<sub>12</sub>E<sub>8</sub>, C<sub>12</sub>E<sub>5</sub>, decane, benzene, CBr<sub>2</sub>H<sub>2</sub>, polysaccharide, micelle, microemulsion, emulsion,Ostwald ripening, NMR,<sup>81</sup>Br,<sup>35</sup>Cl,<sup>2</sup>H, field- dependent spin relaxation, PGSE, selfdiffusion, convection, ringing, thermometer, generalized Blochequations, EXORCYCLE, quadrupole echo, SAXS, WAXS, cryo-TEM.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:kth-3033 |
| Date | January 2000 |
| Creators | Hedin, Niklas |
| Publisher | KTH, Chemistry, Stockholm : Kemi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Trita-FYK, ; 0003 |
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