Deuterium Nuclear Magnetic Resonance Study of Lipophilic Chains in the C12E3/Decane/Water Ternary System

Abstract

The order parameters of lipophilic chains in the liquid crystalline phases of the C12E3/decane/water ternary system have been studied by deuterium NMR spectroscopy. The order parameters derived indicate that the decane molecules added to the C12E3/water system penetrate into the lipophilic alkyl layer of the surfactant and make the structure of the lipophilic layer disordered. The lipophilic layers in the reversed hexagonal phase are more disordered than those in the lamellar phase.

A Combined Raman and Deuterium NMR Spectroscopic Study on the Molecular and Phase Structure of a Nonionic Surfactant C12E5−Water System

“…For aliphatic C−D bonds, the electric field gradient is axially symmetric with its principal axis along the bond direction. Deuterium NMR spectroscopy can thus be an excellent method for studying molecular orientation. − ,− The quadrupole splitting of the two deuterium transitions is given by where δ is 3 / 4 times the quadrupole coupling constant e 2 qQ / h with a value of 167 kHz for aliphatic C−D bonds and θ is the angle between the magnetic field and the principal axis of the electric field gradient tensor, that is, the C−D bond direction. , …”

“…Deuterium NMR spectroscopy can thus be an excellent method for studying molecular orientation. [27][28][29][30][31][32][57][58][59][60][61][62] The quadrupole splitting of the two deuterium transitions is given by where δ is 3 / 4 times the quadrupole coupling constant e 2 qQ/h with a value of 167 kHz for aliphatic C-D bonds and θ is the angle between the magnetic field and the principal axis of the electric field gradient tensor, that is, the C-D bond direction. 61,62 In isotropic phases such as L 1 , L 2 , and V 1 , the surfactant molecules experience rapid isotropic motions, resulting in space averaging of (3 cos 2 θ -1) to effectively zero.…”

“…For studying the order of molecular chains in liquid-crystalline phases, deuterium NMR spectroscopy is one of the powerful experimental techniques. − With this technique, information of motionally averaged C−D bond orientation is obtained through the quadrupole interaction of the deuterium nucleus with the electric field gradient. We have applied this method to studies of the structure of liquid-crystalline phases that contain a nonionic surfactant. − …”

“…We have applied this method to studies of the structure of liquid-crystalline phases that contain a nonionic surfactant. [30][31][32] We propose to combine the two spectroscopies, vibrational spectroscopy and deuterium NMR spectroscopy, to make a comprehensive study of the structure of liquid crystals. An essential advantage of this combination is that the two spectroscopies are complementary in that, while vibrational spectroscopy (infrared and Raman) observes molecular motions on a time scale of 10 -14 to 10 -13 s, NMR spectroscopy observes those on a time scale of 10 -5 to 10 -4 s. In NMR experiments, if the molecular motion is of the order of 10 -15 to 10 -6 s, then the nuclear spins experience motionally averaged spin interactions.…”

“…30 The NMR spectroscopic method was further applied to a ternary system, C 12 E 3 -decane-water. 31 This ternary system was subsequently examined by combined use of the Raman and deuterium NMR spectroscopic methods. 32 In light of the results of these preceding studies, we have performed in this work a combined Raman and deuterium NMR spectroscopic study on the molecular and phase structure of the C 12 E 5 -water system in relation to its phase behavior, where C 12 E 5 denotes CH 3 -(CH 2 ) 11 (OCH 2 CH 2 ) 5 OH (R-dodecyl-ω-hydroxypentakis(oxyethylene)).…”