Theory of the orientational ordering for dimers with conformational flexibility

✍ Scribed by Anna Mercurieva; Tatiana Birshtein

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 512 KB
• Volume: 4
• Category: Article
• ISSN: 1022-1344
• DOI: 10.1002/mats.1995.040040403

✦ Synopsis

Abstract

In the self‐consistent field approximation a theory of the orientational ordering is developed for the melt of dimers containing two mesogenic fragments capable of conformational reorganization. Discrete conformations of the dimers (rotational isomers) are characterized by the values of valence angles. Both three‐dimensional and two‐dimensional melts are considered. It is shown that the presence of bent isomers in the melt reduces the temperature of the phase transition to the anisotropic phase. For a three‐dimensional system with first‐order phase transition to the ordered state, the jump of the order parameter at the transition point for dimers with conformational flexibility appears to be greater than for rigid dimers. For dimers with two isomers (a linear and a bent one) the order parameter and the statistical weight of the linear isomer at the transition point depend nonmonotonously on the statistical weight of this isomer in the isotropic phase. The effect of “supercooling” of the isotropic phase for linear conformations of flexible dimers is discussed.