Self-diffusion NMR

Other important characterization techniques include electrophoresis measurements of droplets [11, 12] (see Section XIV-3C), infrared absorption of the constituent species [13], and light or x-ray scattering. NMR self-diffusion measurements can be used to determine droplet sizes in W/0 emulsions [14]. 

Stepisnik J 1981 Analysis of NMR self-diffusion measurements by a density-matrix oaloulation Physica B/C 104 350-64... 

The last, and less extensively studied field variable driving percolation effects is chemical potential. Salinity was examined in the seminal NMR self-diffusion paper of Clarkson et al. [12] as a component in brine, toluene, and SDS (sodium dodecylsulfate) microemulsions. Decreasing levels of salinity were found to be sufficient to drive the microemulsion microstructure from water-in-oil to irregular bicontinuous to oil-in-water. This paper was... 

B. Balinov, B. Jonsson, P. Linse, O. So-derman 1993, (The NMR self-diffusion method applied to restricted diffusion -simulation of echo attenuation from molecules in spheres and between planes),/. Mag. Reson. A 104, 17. 

K. G. Hollingsworth, A. J. Sederman, C. Buckley, L. F. Gladden, M. L. Johns 2004, (Fast emulsion droplet sizing using NMR self-diffusion measurements), /. Colloid Interface Sci. 274, 244. 

NMR Self-Diffusion of Desmopressin. The NMR-diffusion technique (3,10) offers a convenient way to measure the translational self-diffusion coefficient of molecules in solution and in isotropic liquid crystalline phases. The technique is nonperturbing, in that it does not require the addition of foreign probe molecules or the creation of a concentration-gradient in the sample it is direct in that it does not involve any model dependent assumptions. Obstruction by objects much smaller than the molecular root-mean-square displacement during A (approx 1 pm), lead to a reduced apparent diffusion coefficient in equation (1) (10). Thus, the NMR-diffusion technique offers a fruitful way to study molecular interactions in liquids (11) and the phase structure of liquid crystalline phases (11,12). 

The first part of this review deals with the synthesis and characterization of dendritic aliphatic polyesters based on 2,2-bis(dimethylol)propionic acid (bis-MPA) and 1,1,1 -tris(hydroxyphenyl)ethane (THPE), as core molecule. The convergent growth approach described earlier was applied. We also present H NMR self-diffusion studies of dendrimers of first, second, and third generation. 

From H NMR self-diffusion measurements, the molecular diffusion coefficients could be calculated. Since the diffusion coefficients depend on the size and... 

Soderman et al. [8] gave an overview of NMR self diffusion studies of emulsion systems. They stated that a log-normal distribution function gives a better fit than a normal distribution. Several examples are given including margarine and hydrocarbon gel emulsions. 

Oh et al. [16] have demonstrated that a microemulsion based on a nonionic surfactant is an efficient reaction system for the synthesis of decyl sulfonate from decyl bromide and sodium sulfite (Scheme 1 of Fig. 2). Whereas at room temperature almost no reaction occurred in a two-phase system without surfactant added, the reaction proceeded smoothly in a micro emulsion. A range of microemulsions was tested with the oil-to-water ratio varying between 9 1 and 1 1 and with approximately constant surfactant concentration. NMR self-diffusion measurements showed that the 9 1 ratio gave a water-in-oil microemulsion and the 1 1 ratio a bicontinuous structure. No substantial difference in reaction rate could be seen between the different types of micro emulsions, indicating that the curvature of the oil-water interface was not decisive for the reaction kinetics. More recent studies on the kinetics of hydrolysis reactions in different types of microemulsions showed a considerable dependence of the reaction rate on the oil-water curvature of the micro emulsion, however [17]. This was interpreted as being due to differences in hydrolysis mechanisms for different types of microemulsions. 

Arrhenius plot showing comparison of corrected sorption diffusivities (D0) and NMR self diffusivities (Ds) for A, butane and B, propane in 5A zeolite crystals. (x,o 55pm and 27pm Charnell crystals I. , 34pm and... 

Pulsed-gradient NMR self-diffusion data (22) correlate well with Aeoretical calculations, in which Ae diffusion equation was solved in Ae model geometries by a finite element meAod (Anderson, D. M. Wennerstrdm, H., in preparation) ... 

Stepisnik, J. (1981). Analysis of NMR self-diffusion measurements by density matrix calculation. Physica B 104, 350-364. 

Stepisnik, J. (1995). Violation of the gradient approximation in NMR self-diffusion measurements. Z. Phys. Chem. 190, 51-62. 

According to Eqs. (4)-(6), the molecular mean square displacements and thus the self-diffusion coefficients may be determined from the slope of a semilogarithmic plot of the PFG NMR signal F versus (Sg) The observation time of self-diffusion is the separation between the two field gradient pulses, t. Owing to their relatively large gyromagnetic ratio and to their natural abundance of 1, protons provide very suitable conditions for NMR self-diffusion studies, but C 44), F 45), and Xe 46-48) resonances have also been used successfully in recent PFG NMR studies of zeolites. 

C. Analysis of Molecular Translations and Rotations by Combined H NMR Relaxation and NMR Self-Diffusion Studies... 

B. Combined H NMR Relaxation and Pulsed-Field Gradient NMR Self-diffusion Studies for Propane in ZSM-5 AND NaX... 

NMR Self-Diffusion in Binary Mixtures Using Deuterated Compounds... 

---