The Frustrated Spin-Gas Theory of Multiply Reentrant Liquid Crystals
Quadruply reentrant phase diagrams (nematic↔smectic Ad ↔ nematic ↔ smectic Ad ↔ nematic ↔ smectic A1), smectic layer thicknesses, and transition enthalpies have been obtained from the frustrated spin-gas model, in satisfactory agreement with experiments. The stringent requirement on the molecular tail length for quadruple reentrance, seen in experiments, also occurs in this theory. The microscopic mechanism underlying the two smectic Ad peninsulae is found to be relief of dipolar frustration by permeation either on atomic length scale, or on librational length scale, respectively, at higher or lower temperatures. The distinctive transition enthalpies can be related to the molecular dimers, which form a nematic background in the smectic Ad phase, but which break up at the onset of the smectic Al phase.
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- 5.J. O. Indekeu and A. N. Berker, M.I.T. preprint (1987)Google Scholar
- 13.In retrospect, this microscopic model could be more aptly referred to as the “frustrated spin-liquid”! We shall continue the spin-gas appellation for historic reason (Ref. 1).Google Scholar
- 15.This theoretical prediction was subsequently confirmed experimentally by Ref. 11.Google Scholar
- 16.Most basically, as presumed quite generally, molecular tails delay crystallization upon cooling and make liquid crystal phases possible.Google Scholar
- 18.K. W. Evans-Lutterodt, J. W. Chung, R. J. Birgeneau, J. W. Goodby, and C. W. Garland (to be published).Google Scholar
- 19.N. H. Tinh, G. Sigaud, M. F. Achard, H. Gasparoux, and F. Hardouin, in “Advances in Liquid Crystal Research and Applications,” ed. L. Bata (Pergamon, Oxford, 1980), p.147.Google Scholar
- 20.B. R. Ratna, R. Shashidhar, and K. V. Rao, in “Proceedings of the International Liquid Crystal Conference,” Bangalore (1979). These results are also exhibited in S. Chandrasekhar, Mol. Cryst. Liq. Cryst. 124, 1 (1985).Google Scholar