Competition in low ordered smectics between incommensurate phases and two-dimensional modulated ones for dimesogenic compounds

Research paper by F. Hardouin, M.F. Achard, J.-I. Jin, Y.-K. Yun, S.-J. Chung

Indexed on: 01 Jan '98Published on: 01 Jan '98Published in: The European Physical Journal B


Systematic physical chemistry studies are in progress concerning the occurrence of incommensurate low ordered smectic phases \(\) in non-symmetric dimesogens varying molecular parameters from the standard compound KI-5. In the present study, the selected molecules possess the same spacer length and the same cholesteryl unit. By means of X-ray diffraction on orientated samples, commensurate phases, incommensurate fluid smectics and two-dimensional ones are clearly evidenced depending both on temperature and molecular parameters. So these dimesogenic compounds respond to the frustration connected to the competition between two incommensurate lengths with the formation either of an incommensurate phase \(\) or of a two-dimensional modulated phase. A new topology in a phase diagram results from this competition in a binary system composed of two homologous dimesogens.