Mesomorphism in the System Disodium Chromoglycate-Water

作者：Norman Holt Hartshorne, G. D. Woodard · 发表于：Molecular crystals and liquid crystals · 年份：1973 · DOI：10.1080/15421407308083381 · 被引用次数：153 · 研究领域：Liquid Crystal Research Advancements、Molecular spectroscopy and chirality、Surfactants and Colloidal Systems

The system has been studied by a combination of polarization microscopy, using a hot stage, and X-ray diffraction analysis. The sequence of condensed phases occurring at room temperature with increasing concentration of disodium chromoglycate (DSCG) is: (i) a mesophase N; (ii) a mesophase M; (iii) crystalline solid solutions SS. A variety of evidence has shown that the molecule of DSCG retains an essentially planar configuration throughout the system. The mesomorphic phases are optically negative, indicating a parallel, or approximately parallel, arrangement of the molecular planes. (A parallel arrangement of these planes in the SS solid solutions had been previously indicated by a preliminary X-ray analysis, which pointed to there being only one molecule in the unit cell; and in conformity with such an arrangement the crystals were found to be optically negative.) The transformations between the N and M phases and between the M and SS phases take place pseudomorphically, and on reversal the original textures are recovered. The N phase appears to be genuinely nematic in structure, in contrast to other cases of lyotropic systems showing nematic-like textures that have been reported, but which are believed to be deformed lamellar phases. The M phase gives X-ray reflections corresponding to a “middle” structure, of the M 1 type, i.e., one in which the DSCG is clustered into rods separated by a water continuum, and with the polar —COONa groups occupying the surfaces of the rods. ...