Low-temperature phase separation of a binary liquid mixture in porous materials studied by cryoporometry and pulsed-field-gradient NMR

The low-temperature liquid-liquid phase separation of the partially miscible hexane-nitrobenzene mixture imbibed in porous glasses of different pore sizes from 7 to 130 nm has been studied using 1H NMR (nuclear magnetic resonance) cryoporometry and pulse field gradient NMR methods. The mixture was quenched below both its upper critical solution temperature (T cr) and the freezing point of nitrobenzene. The size distribution of frozen nitrobenzene domains was derived through their melting point suppression according to the Gibbs-Thompson relation. The obtained data reveal small initial droplets of nitrobenzene surrounded by hexane, which are created as the temperature is decreased below Tcr and which thereafter coalesce by a droplet-diffusion mechanism. The inter-relation between the pore size and the found size distribution and shapes of nitrobenzene domains is discussed, as well as several aspects of molecular self-diffusion. © 2002 The American Physical Society

Acceleration of diffusion in ethylammonium nitrate ionic liquid confined between parallel glass plates

The bulk self diffusion of the ethylammonium cation and the nitrate anion can both be described by respective single diffusion coefficients. Diffusion of the anion is 1.7 times higher than that of the cation. This indicates no tight association of the ions in the ionic liquid. For the ethylammonium cation confined between glass plates the effective diffusion coefficient along, as well as normal to the confining glass plates is higher by a factor of 1.86 as compared to that in the bulk. The same time, NMR T2 relaxation of protons of NH3 group of the EA cation is faster by a factor of 22 than that in bulk. 2H NMR spectra of selectively labeled CH2 and CH3 groups of EA do not demonstrate any ordering of the EA between the glass plates. We suggested that these data favor a model where a bulk isotropic sponge like structure of EAN is saved in the confinement, but sizes of connecting channels increases. Those leads to faster translational diffusion and faster exchange processes of protons of NH3 group, in comparison with the bulk.Comment: 11 pages, 5 figures, 1 tabl

Liquid-liquid phase separation in micropores

Phase separation of binary liquids with an upper critical temperature in porous materials is studied by 1H NMR cryoporometry and cross-relaxation spectroscopy and by 15N NMR spectroscopy. The first method provides domain size distributions of the separating minority component while the other ones verify the segregation of the two liquids on molecular level. We find that metastable structures are formed manifested by bimodal domain size distributions. The kinetic arrest of domain growth may be imposed upon by bottlenecks in the porous structure that block diffusion of entire droplets. Practical applications, if one of the liquid components is polymerized, include mobile polymer particles trapped in porous matrix that can serve, e.g., as filters with microscopically amphiphilic pathways. © 2003 Elsevier B.V. All rights reserved

Acceleration of diffusion in ethylammonium nitrate ionic liquid confined between parallel glass plates

© the Owner Societies 2017. Diffusion of EAN confined between polar glass plates separated by a few micrometers is higher by a factor of ca. 2 as compared to bulk values. Formation of a new phase, different to the bulk, was suggested

Low-temperature phase separation of a binary liquid mixture in porous materials studied by cryoporometry and pulsed-field-gradient NMR

The low-temperature liquid-liquid phase separation of the partially miscible hexane-nitrobenzene mixture imbibed in porous glasses of different pore sizes from 7 to 130 nm has been studied using 1H NMR (nuclear magnetic resonance) cryoporometry and pulse field gradient NMR methods. The mixture was quenched below both its upper critical solution temperature (T cr) and the freezing point of nitrobenzene. The size distribution of frozen nitrobenzene domains was derived through their melting point suppression according to the Gibbs-Thompson relation. The obtained data reveal small initial droplets of nitrobenzene surrounded by hexane, which are created as the temperature is decreased below Tcr and which thereafter coalesce by a droplet-diffusion mechanism. The inter-relation between the pore size and the found size distribution and shapes of nitrobenzene domains is discussed, as well as several aspects of molecular self-diffusion. © 2002 The American Physical Society

4-ethylsulphonylnaphthalene-1-sulphonamide (hpa).

The low-temperature liquid-liquid phase separation of the partially miscible hexane-nitrobenzene mixture imbibed in porous glasses of different pore sizes from 7 to 130 nm has been studied using 1H NMR (nuclear magnetic resonance) cryoporometry and pulse field gradient NMR methods. The mixture was quenched below both its upper critical solution temperature (T cr) and the freezing point of nitrobenzene. The size distribution of frozen nitrobenzene domains was derived through their melting point suppression according to the Gibbs-Thompson relation. The obtained data reveal small initial droplets of nitrobenzene surrounded by hexane, which are created as the temperature is decreased below Tcr and which thereafter coalesce by a droplet-diffusion mechanism. The inter-relation between the pore size and the found size distribution and shapes of nitrobenzene domains is discussed, as well as several aspects of molecular self-diffusion. © 2002 The American Physical Society