14N NMR spectra of molecular nitrogen in SDS/pentanol swollen lamellar phases

Abstract

14N NMR spectra of air dissolved in lyotropic mesophases are reported. In order to observe the whole spectrum from a molecule in which the quadrupole coupling constant is on the order of a few megahertz, a weak alignment degree with respect to the magnetic field is mandatory. Therefore, dilute lyotropic liquid crystals, namely sodium dodecylsulphate (SDS)/pentanol swollen lamellar phases, were considered. The temperature dependence of the 14N quadrupolar splitting was followed both in the case of oil (either n-dodecane or n-heptane) and brine (a 0.2-M NaBr water solution) swelling. In the former, it paralleled the temperature dependence of the splittings of the alkane deuteria and, in both cases, it was opposite to 23Na quadrupolar splittings. Owing to the higher N2 solubility in hydrocarbons, the 14N NMR spectra provide complementary information to that obtained by means of the quadrupolar nuclei of water and hydrophilic solutes.

Using solution state NMR spectroscopy to probe NMR invisible gelators

“…[17][18][19][20] Results and discussion Functionalised dipeptides can be extremely effective gelators. [17][18][19][20] Results and discussion Functionalised dipeptides can be extremely effective gelators.…”

“…Approaches similar to ours have been used to glean valuable information on surface-solute interactions in a variety of systems including clays and liquid crystals. [17][18][19][20]…”

Nuclear magnetic resonance: a powerful tool to study liquid crystals

“…Figure 2 (a)). Recent advancements in the field of liquid crystals, such as the understanding of the director reorientational behaviour in nematic phases in presence of the electric field [9], the explanation of the supramolecular structure of the twisted nematic phase [10] [16]. Papers focused on these nuclei represent more than 33% of total papers published in the last 50 years (see Figure 2(a)).…”

A Photosensitive Liquid Crystal Studied by 14N NMR, 2H NMR, and DFT Calculations

“…The mesomorphic behaviour, in the absence of UV illumination, is reported in Figure 1 and it is characterized by a nematic phase and a monotropic smectic A phase that can be supercooled down to room temperature. [26] The trans-to-cis photoisomerization of 7AB suppresses the liquid crystalline phase, thus enabling the material to remain in the isotropic phase even at room temperature. For our NMR study, the 7AB sample was melted in a quartz tube with a diameter of 5 mm in order to fill an internal volume of about 230 mm 3 .…”

“…In liquid crystals, 14 N NMR resonance has so far been detected only rarely, both in lyotropic [22][23][24][25][26] and thermotropic [27,28] liquid crystals. The reason lies in the relatively large quadrupolar coupling of the 14 N nucleus, resulting in broad NMR spectra and spin-lattice relaxation times in the range of several microseconds.…”