| Popis: |
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 orig... |
