Diffusion ordered nuclear magnetic resonance spectroscopy: principles and applications

Translational motion in solution, either diffusion or fluid flow, is at the heart of chemical and biochemical reactivity. Nuclear Magnetic Resonance (NMR) provides a powerful non-invasive technique for studying the phenomena using magnetic field gradient methods. Describing the physical basis of measurement techniques, with particular emphasis on diffusion, balancing theory with experimental observations and assuming little mathematical knowledge, this is a strong, yet accessible, introduction to the field. A detailed discussion of magnetic field gradient methods applied to Magnetic Resonance Imaging (MRI) is included, alongside extensive referencing throughout, providing a timely, definitive book to the subject, ideal for researchers in the fields of physics, chemistry and biology.

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NMR Studies of Translational Motion

NMR studies of complex surfactant systems

The complexation between a charged micelle and an oppositely charged polyelectrolyte was studied by using a simple model system with a particular emphasis on the electrostatic interaction and the polyelectrolyte rigidity. Structural data of the micelle−polyelectrolyte complex and thermodynamic quantities of the complexation as a function of the flexibility of the polyelectrolyte were obtained by using Monte Carlo simulation and thermodynamic integration. Moreover, the ratio of the critical aggregation concentration, cac, and the critical micellization concentration, cmc, was calculated, cac being the lowest surfactant concentration at which the surfactants self-aggregate in the presence of polyelectrolyte. The cac was found to be ca. 4 (rigid polyelectrolyte) to ca. 60 (flexible polyelectrolyte) times lower than the cmc. The latter value is in line with experimental data of similar systems. Hence, it seems that the electrostatic interactions as well as the rigidity of the polyelectrolyte are important fac...

Monte Carlo Simulations of Polyelectrolytes at Charged Micelles. 1. Effects of Chain Flexibility

The article reviews water-soluble polymers characterized by surfactant side chains, and related amphiphilic polymers. Various synthetic approaches are presented, and rules for useful molecular architectures are given. Models for the self-organization of such polymers in water are presented comparing them with the micellization of low molecular weight surfactants. Highlighting key properties of aqueous polysoap solutions such as viscosity, surface tension and solubilization power, some structure-property relationships are established. Further, the formation of mesophases and of superstructures in bulk is addressed. Finally, the functionalization of polysoaps, and potential applications are discussed.

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Molecular concepts, self-organisation and properties of polysoaps

In the first systematic application of the two-dimensional quadrupolar echo (2DQE) method, we study the {sup 23}Na NMR relaxation behavior of counterions in the reversed hexagonal mesophase of the AOT/D{sub 2}O/isooctane system, consisting of long cylindrical aggregates with the water and ions on the inside. Using a combination of relaxation experiments, performed on magnetically aligned samples, we determine the three spectral densities at two sample orientations. The orientational dependence of the spectra densities allows us to separate contributions from different types of molecular motion.

Counterion surface diffusion in a lyotropic mesophase: a sodium-23 two-dimensional quadrupolar echo NMR relaxation study

The response, in the frequency domain, of half‐integral spin I>1 nuclei in anisotropic systems to the quadrupolar echo (QE) pulse sequence (π/2)x−τ−(π/2)y is investigated, with particular emphasis on the effects of quadrupolar relaxation. Using a state multipole formalism, we derive the frequency spectra produced by one‐ or two‐dimensional Fourier transformation. Powder samples as well as uniformly and partially oriented samples are considered. The 2D QE experiment produces, in the F1 dimension (Fourier transformation with respect to τ), spectra which provide information about the static quadrupole coupling even if only the central line in the QE spectrum (obtained by Fourier transformation of the induction signal after the echo) is detected. For partially oriented and (incompletely dephased) powder samples, the F1 spectra allow the motional spectral densities to be determined with little or no effect of the inhomogeneous quadrupole coupling, which severely complicates the analysis of conventional (single...

Spin relaxation of I>1 nuclei in anisotropic systems. I. Two‐dimensional quadrupolar echo Fourier spectroscopy

A 2H n.m.r. relaxation study of sodium dodecyl sulphate (SDS) in the micellar phase is presented. The surfactant is specifically deuterated in the α-, γ- and ω-positions. Relaxation data are obtained at two temperatures and at three field strengths, and show a dependence on the field strength. The data are analysed with the ‘two-step’ model of relaxation, and the fast correlation times as well as the order parameters for the three deuterated positions on the hydrocarbon chain are presented. The order parameters obtained are very similar in magnitude to those found in the SDS/water hexagonal phase. In particular, the order parameter is very low (ca. 0.03) for the ω-methyl deuterons. In addition, a common slow correlation time is obtained from the data. The slow correlation time is discussed in terms of the micellar rotational tumbling process and surfactant lateral diffusion along the micellar surface, and a value for the diffusion coefficient of the latter process is obtained.

Nuclear magnetic resonance relaxation in micelles. Deuterium relaxation at three field strengths of three positions on the alkyl chain of sodium dodecyl sulphate

Determination de la dimension des micelles, du nombre d'agregation et la capacite de solubilisation des solutions micellaires

Hydrocarbon chain conformation of bipolar surfactants in micelles. A magnetic field-dependent carbon-13 and nitrogen-14 NMR spin-lattice relaxation and nuclear Overhauser effect study of N,N'-1,20-eicosanediylbis(triethylammonium bromide)

published in Advance ACS Abstracts, January 1, 1994. 0022-3654/94/2098-0603%04.50/0 determining phase structure, ion binding, and the size of the aggregates in organized solutions1416 and is thus a powerful technique for the study of polymer/surfactant systems. Recently, Johnson and co-workers developed a new pulsed-field-gradient NMR diffusion technique, diffusion-ordered 2D NMR spec- troscopy (DOSY).17 The application of DOSY to surfactant, vesicles, and polymer systems has also been demonstrated in subsequent investigations.l* In this paper, the application of the DOSY technique to the study of the non-Newtonian to Newtonian transition and the binding of the salicylate ions of the CTAB/ NaSal/D20 system as a function of the content of the polymer, PVME, are reported. Experimental Section Materials and Samples. CTAB was obtained from Aldrich Chemicals, NaSal from Mallinkrodt. PVME in the form of 50% (by weight) aqueous solution was obtained from Aldrich Chem- icals; D20 (99.9%) was obtained from Isotec, Inc. All chemicals were used as received without further purification. The average molecular weight of PVME obtained from the same source was determined to be

Tuck C. Wong

Papers

Counterion surface diffusion in a lyotropic mesophase: a sodium-23 two-dimensional quadrupolar echo NMR relaxation study

Spin relaxation of I>1 nuclei in anisotropic systems. I. Two‐dimensional quadrupolar echo Fourier spectroscopy

Nuclear magnetic resonance relaxation in micelles. Deuterium relaxation at three field strengths of three positions on the alkyl chain of sodium dodecyl sulphate

Hydrocarbon chain conformation of bipolar surfactants in micelles. A magnetic field-dependent carbon-13 and nitrogen-14 NMR spin-lattice relaxation and nuclear Overhauser effect study of N,N'-1,20-eicosanediylbis(triethylammonium bromide)

Polymer-Induced Non-Newtonian to Newtonian Transition in the Viscoelastic CTAB/Sodium Salicylate/Water System As Studied by Diffusion-Ordered 2D NMR