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  • 1
    Electronic Resource
    Electronic Resource
    Counterion surface diffusion in a lyotropic mesophase: a sodium-23 two-dimensional quadrupolar echo NMR relaxation study (1990)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 94 (1990), S. 2600-2613 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100369a070
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  • 2
    Electronic Resource
    Electronic Resource
    Micelle size and order in lyotropic nematic phases from nuclear spin relaxation (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 3875-3891 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nuclear magnetic resonance (NMR) relaxation of quadrupolar nuclei is introduced as a new method for determining micelle size and nematic order in lyotropic nematic mesophases from the dependence of the spin relaxation rates on molecular diffusion over the curved micelle surface. The approach is illustrated by an experimental study of two uniaxial nematic phases (the calamitic NC and discotic ND phases of the sodium dodecyl sulphate/decanol/water system) using two nuclei: 2H in the α-deuterated surfactant and 23Na in the counterions. The two nuclei yield similar results: an apparently temperature independent axial ratio of 3–4 in both phases and a nematic order parameter which decreases from ca. 0.9 (0.75) at the lowest temperature to ca. 0.6 (0.5) at the highest temperature in the NC (ND) phase. As compared to the predictions of the Maier–Saupe theory, the nematic order parameter in the NC phase is considerably larger and decreases more strongly as the nematic–isotropic transition is approached.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461892
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear spin relaxation in a hexagonal lyotropic liquid crystal (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6945-6961 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The hexagonal (E) phase in the sodium dodecyl sulphate (SDS)/decanol/water system is investigated by 2H and 23Na nuclear magnetic resonance (NMR) of the selectively deuterated SDS and the sodium counterion. Using macroscopically oriented E phase samples, prepared from the magnetically aligned nematic (NC) phase, we measure the orientation-dependent relaxation rates R1Z and R1Q as well as the line shape of both nuclei. The orientation dependence of the lab-frame spectral densities, determined from the relaxation rates, allow us to separate contributions from different types of molecular motion. In particular, we find a dominant contribution from molecular diffusion around the cylindrical aggregate. From this contribution we determine the lateral diffusion coefficient of SDS to (1.4±0.2)×10−10 m2 s−1 at 25 °C (activation energy 26±2 kJ mol−1 ) and the counterion surface diffusion coefficient to (4.8±0.9)×10−10 m2 s−1 at 25 °C (a factor 2.8 smaller than in an infinitely dilute aqueous electrolyte solution). Furthermore, the flexibility of the cylindrical aggregates in the investigated E phase (aggregate volume fraction 0.27) is quantified in terms of an orientational order parameter SDC≈0.9.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461506
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  • 4
    Electronic Resource
    Electronic Resource
    Spin relaxation of I〉1 nuclei in anisotropic systems. II. Inversion recovery and even-rank polarization decay (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 42-51 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The response of half-integral spin I〉1 nuclei in anisotropic systems to pulse sequences that probe longitudinal quadrupolar relaxation is investigated. The dynamical coupling among polarizations of different rank renders the response more complicated than in the case of I=1 nuclei. Nevertheless, for I=3/2 and I=5/2 nuclei, exponential or biexponential spectral decays can be produced that enable accurate determination of the motional spectral densities j1 and j2. While the inversion recovery experiment, which probes the evolution of the odd-rank polarizations, is useful mainly for I=3/2, the decay of the even-rank polarizations is conveniently analyzed also for I=5/2. We thus describe pulse sequences, analogous to the Jeener–Broekaert sequence for I=1, that yield exponential decay for I=3/2 and biexponential (sum or difference) decay for I=5/2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457477
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  • 5
    Electronic Resource
    Electronic Resource
    Spin relaxation of I〉1 nuclei in anisotropic systems. I. Two-dimensional quadrupolar echo Fourier spectroscopy (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5382-5397 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: 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-pulse) and QE spectra. For completely dephased powder samples (large splittings), the last of the multiple spin echoes gives rise to a triplet QE spectrum (for any I≥3/2), the satellite decay in which yields a transverse relaxation rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455589
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  • 6
    Electronic Resource
    Electronic Resource
    Phase separation of a binary liquid mixture in porous media studied by nuclear magnetic resonance cryoporometry (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 1072-1076 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: 1H nuclear magnetic resonance cryoporometry has been applied to study the low-temperature phase separation of the two components in a binary liquid imbibed in porous glass. The mixture of hexane and nitrobenzene was quenched below both its upper critical temperature and the freezing point of the nitrobenzene. The size distribution of phase-separated liquid domains was observed through their melting point suppression that reveals small droplets of nitrobenzene surrounded by hexane within the pores. If the bottlenecks of the porous network allow, some of these droplets coalesce and thereby completely fill parts of the network. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1427706
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  • 7
    Electronic Resource
    Electronic Resource
    The morphology of coexisting liquid and frozen phases in porous materials as revealed by exchange of nuclear spin magnetization followed by 1H nuclear magnetic resonance (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 2307-2316 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: At low temperatures, liquids imbibed into nanoporous materials form frozen solid cores in the interior of pores. Inbetween the cores and the pore walls, there exists a layer of nonfrozen liquid. As demonstrated here by nuclear magnetic resonance magnetization transfer and cryoporometry experiments, pools of nuclear spins that reside in those two separate domains, core and liquid layer, exchange nuclear Zeeman magnetization. This exchange is detectable in these materials thanks to the high contact area. Based on this phenomenon, we propose a new method for measuring the surface-to-volume ratio and for accessing the pore space morphology in nanoporous materials. By monitoring the magnetization transfer process, information can be obtained: (i) on the geometrical characteristics of the porous space and (ii) on the diffusivity of nuclear magnetization in the frozen phase. The diffusive transport of nuclear magnetization in the frozen core can be contributed by two mechanisms: spatial atomic/molecular diffusion and spin diffusion through nuclear dipole–dipole interaction. For the water–ice system in controlled porous glasses of known morphology, we can separate these two mechanisms to obtain an estimate of the proton diffusion coefficient of 4×10−16 m2/s in ice at 255 K. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1488585
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  • 8
    Electronic Resource
    Electronic Resource
    127I-NMR studies of anion binding to κ-carrageenan (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1709-1714 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A preliminary 127I-NMR relaxation study of the binding of the I- ion to κ-carrageenan is presented. Signal loss caused by motional correlation times out of extreme narrowing makes it difficult to analyze line widths. Longitudinal relaxation times are more suitable for a comprehensive relaxation study. From the observation of nonextreme motional narrowing, the lower limit of the residence time at the binding site is estimated to be on the order of 10 ns. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360331108
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  • 9
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    Low-temperature phase separation of a binary liquid mixture in porous materials studied by cryoporometry and pulsed-field-gradient NMR (2002)
    American Physical Society
    Details
    Publication Date: 2002-09-25
    Print ISSN: 1063-651X
    Electronic ISSN: 1095-3787
    Topics: Physics
    Published by American Physical Society
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  • 10
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    The Effect of Partial Acylglycerols on the Exchange Between Liquid and Solid Tripalmitoylglycerol (2007)
    Wiley
    Details
    Publication Date: 2007-03-13
    Print ISSN: 0003-021X
    Electronic ISSN: 1558-9331
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley
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