Eur. Phys. J. B 1, 47-56 (1998)
https://doi.org/10.1007/s100510050151

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

¹ Centre de Recherche Paul Pascal, Université Bordeaux I, avenue A. Schweitzer, 33600 Pessac, France
² Department of Chemistry, College of Sciences, Korea University, Seoul 136-701, Korea

Corresponding author: ^a f.hardouin@presidence-bx1.u-bordeaux.fr

Received: 26 June 1997
Revised: 7 October 1997
Accepted: 29 October 1997
Published online: 15 January 1998

Abstract

Systematic physical chemistry studies are in progress concerning the occurrence of incommensurate low ordered smectic phases (S_ic) 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 S_ic 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.