Recent theories have suggested that mutual diffusion between miscible polymers may be strongly influenced by the unusual thermodynamics of mixing of high polymers; in addition the mobility properties of polymer blends are not, in general well understood. This dissertation describes experiments to investigate how these factors influence mutual diffusion in miscible polymer blends. After a general introduction and a review of some recent theories of mutual diffusion in polymer blends, experiments are described in one miscible blend system, Polyvinyl Chloride (PVC)/Polycaprolactone (PCL);x-ray microanalysis in a scanning electron microscope was used to measure the concentration dependence of the mutual diffusion coefficient. To explain this concentration dependence we need to invoke not only the thermodynamics of mixing but also the dependence on composition of the monometric friction coefficients in the system. This dependence was investigated using an ESR spin probe technique. The final section of the dissertation deals with an attempt to use the potentially powerful ion beam analysis techniques of Rutherford Backscattering (RBS) and Forward Recoil scattering (FReS) to measure mutual diffusion coefficients, as well as intradiffusion coefficients (whose concentration dependence should not be influenced by thermodynamic effects). Results obtained by these techniques are presented for three blend systems, including PVC/PCL; the results by RBS for the latter system are consistent with the results obtained by x-ray microanalysis.

The specific goal of the investigation was the measurement, as a function of temperature, of the self-diffusion coefficients of Pb210 and Cl36 in PbCl2-KCl compositions in the region of the first compound, and to calculate from these data the activation energy necessary for the diffusion of these ions.

This work is an extension of Yin's work studying the diffusion of Na ion in the PbCl2-NaCl system, but at more dilute compositions of NaCl.

No description available.

The primary aim of this thesis is to investigate and quantify the self-diffusion processes of gaseous molecules adsorbed in industrially relevant microporous zeolite materials using Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR). The main body of this work involves the use of weakly adsorbing hydrocarbon gases (CH4, C2H6 and C3H¬8) adsorbed in a large pore β-zeolite structure. This thesis describes the development of a solely PFG NMR based technique for measuring the molecular displacements of these species at varying length-scales. This enabled the characterisation of self-diffusion regimes across zeolite beds and within individual zeolite crystallites. The characterisation of self-diffusion processes within single zeolite crystallites was critical with respect to accounting for quantitative discrepancies reported in the literature between PFG NMR and alternative measurement techniques. This approach also revealed that the transitions in the Gaussian probability distributions of the molecular displacements in the aforementioned self-diffusion regimes could be recorded by varying the experimental time-scale for observing molecular motion. This technique was extended to characterise the self-diffusion processes of the aforementioned hydrocarbons in small (≤ 1 μm) and large (≥ 15 μm) zeolite crystallites to investigate the dependence of this technique on zeolite geometry. It was found that the self-diffusion coefficients within single crystallites were in good agreement with one another, despite their differing crystallite geometries. This technique was subsequently used to study the self-diffusion behaviour of two-component hydrocarbon gaseous mixtures with differing sorption properties co-adsorbed in β-zeolite. Excellent chemical shift resolution was obtained for chemically similar species using NMR spectroscopy, relaxometry and diffusometry without the use of Magic Angle Spinning (MAS). This connoted that conventional PFG NMR is capable of precisely characterising individual species in real world multi-component systems. This thesis also describes the self-diffusion of ammonia in small pore chabazite structures, which are typically used in Selective Catalytic Reduction (SCR) processes. It was found that the self-diffusion coefficient of this strongly adsorbing species increased with molecular loading up to a certain point. This peculiar behaviour implied a strong concentration and inter-molecular dependence within the zeolite structure. Lastly, the techniques which were developed at high magnetic field strengths (300 MHz) were transferred to a lower field strength (43 MHz) benchtop spectrometer at the Johnson Matthey Technology Centre (JMTC). This describes the first characterisation of mass transport behaviour of weakly interacting sorbates in zeolites using a portable spectrometer. This presents an excellent opportunity for future off-line molecular displacement measurements to be made for complex and real-world systems in a matter of minutes.

The self-diffusion coefficient of a polymer in solution may be expanded in the concentration of the polymer, as seen in equation 1. The linear term would represent a perturbation due to the presence of another polymer; the c^{2} term would represent a perturbation due to interactions of trios of polymers. Phillies determined the c^{2} term of a virial expansion of the self-diffusion coefficient for trios of polymers interacting via a ring. Here I determine a correction to the c^{2} term due to trios of polymers interacting via a figure-eight scattering diagram: the equivalent of four polymers interacting in a ring where the second polymer and the fourth polymer are the same. D_{s}(c) = D_{0}(1+ alpha D_{0} c + beta D_{0}^{2}c^{2}+...) 1 or, D_{s}(c) = D_{0}(1+ alpha D_{s}(c)c). 2 A D_{0} may be replaced by D_{s}(c) in equation 1 to arrive at equation 2. The left-hand-side of equation 2 is the final self-diffusion coefficient, and the D_{s}(c) on the right-hand-side of this equation is that due to the question of self-similarity. If the D_{s}(c) on the right-hand-side is given by equation 1, resulting in beta=alpha^{2}, it may be said that the system exhibits self-similarity. I demonstrate self-similarity quantitatively for a polymer solution using a generalized Kirkwood-Riseman model of polymer dynamics. The major physical assumption of the model I utilize to derive equation 2 is that, in solution, polymer motions are dominantly governed by hydrodynamic interactions between the chains. First, I review the Kirkwood-Riseman model for intrachain hydrodynamic interactions. I then discuss Phillies' extension of this model to interchain interactions for duos or trios of polymers in a ring. I analytically calculate the hydrodynamic interaction tensor from a multiple scattering picture T_{54321}, for five polymers in solution and verify this tensor by numerical differentiation. Finally, I perform the ensemble average of the self-interaction tensor b_{1232} appropriate to the figure-eight scattering diagram both analytically and with a Monte Carlo routine, thereby verifying equation 2 to second order in concentration.

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 CBr2H2dissolved 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. Field-dependent81Br and35Cl NMR relaxation studies in micellar solutions ofC16TAX 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-dependent2H NMR relaxation study on the CTABr-α-d2and benzene-d6showed 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 C12E8-D2O system showed monotonous growth of the micellesupon increasing temperature. Emulsion droplets in the C12E5-decane-D2O system where shown to coarsen according to theOstwald ripening theory after being brought out of equilibriumby a temperature drop. X-ray scattering and2H NMR line-shape and relaxation experimentssuggested that complex solids formed by a partly-sulfatedpolysaccharide and CnTAB exhibit regular ordering at both microscopicand mesoscopic length scales. <b>Keywords</b>: CTAB, CTAC, C12E8, C12E5, decane, benzene, CBr2H2, polysaccharide, micelle, microemulsion, emulsion,Ostwald ripening, NMR,81Br,35Cl,2H, field- dependent spin relaxation, PGSE, selfdiffusion, convection, ringing, thermometer, generalized Blochequations, EXORCYCLE, quadrupole echo, SAXS, WAXS, cryo-TEM.

<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 CBr₂H₂dissolved 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-dependent⁸¹Br and³⁵Cl NMR relaxation studies in micellar solutions ofC₁₆TAX 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-dependent²H 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 C₁₂E₈-D₂O system showed monotonous growth of the micellesupon increasing temperature. Emulsion droplets in the C₁₂E₅-decane-D₂O system where shown to coarsen according to theOstwald ripening theory after being brought out of equilibriumby a temperature drop. X-ray scattering and²H NMR line-shape and relaxation experimentssuggested that complex solids formed by a partly-sulfatedpolysaccharide and C_nTAB exhibit regular ordering at both microscopicand mesoscopic length scales.</p><p><b>Keywords</b>: CTAB, CTAC, C₁₂E₈, C₁₂E₅, decane, benzene, CBr₂H₂, polysaccharide, micelle, microemulsion, emulsion,Ostwald ripening, NMR,⁸¹Br,³⁵Cl,²H, field- dependent spin relaxation, PGSE, selfdiffusion, convection, ringing, thermometer, generalized Blochequations, EXORCYCLE, quadrupole echo, SAXS, WAXS, cryo-TEM.</p>

Self-diffusion coefficients give insight into the mobility of molecular species and serve as benchmark variables for molecular modeling. Nuclear magnetic resonance (NMR) spectroscopy is an excellent method for the measurement of self-diffusion coefficients: In the present work, a pulsed gradient stimulated echo (PGSTE) pulse sequence was employed for their determination in binary and ternary liquid systems at 298 K and 1 bar. To ensure a high quality of the measurements, a preliminary gradient mapping was carried out. The experimental results are compared to molecular simulation data by Guevara-Carrion et al. [1] for binary systems (acetone/toluene, acetone/ethanol and acetone/cyclohexane) and to molecular simulation data that was determined in the present work for the ternary system acetone/toluene/cyclohexane.

The specific goal of this investigation was the determination of the self-diffusion coefficient of the divalent lead ion in a fused lead chloride system at several temperatures and the determination of the activation energy for the diffusion process.