Intermediate Liquid Crystalline Phases in the Binary System C16TACl-H2O: An NMR and Low-Angle X-ray Diffraction Study

Article abstract of DOI:10.1021/j100188a059

The liquid crystalline phases formed in the concentration range between the hexagonal and the lamellar phase in the binary system C16TACl-H2O have been studied by 2H, 14N, and 35Cl NMR, low-angle X-ray diffraction and optical microscopy.A cubic phase and three anisotropic so-called intermediate phases have been found.At 45 deg C the hexagonal phase is stable up to 75 wt percent C16TACl.Between 75 percent and 79 percent, a biaxial phase (Int-1) built up by long rods with noncircular cross sections is formed.From the asymmetry parameter of the time-averaged electric field gradient tensor the axial ratio of the cross section was found to increase from ca. 1.15 to ca. 1.4 with increasing concentration.In the range 80-83 percent a second intermediate phase (Int-2) is formed with a smaller quadrupole splitting than in the hexagonal phase and with an asymmetry parameter close to 1.A third intermediate phase (Int-3) was detected in some samples.This uniaxial phase has a very small quadrupole splitting (4.4 kHz for 2H in the α-methylene segment).It is suggested that the Int-2 and Int-3 phases are built up by noncubic periodic minimal surfaces, e.g., tetragonally, rhomboedrally, or orthorhombically distorted P or D surfaces.