Pretransitional behavior

Our illustration of pretransitional behavior in frustrated NLC systems is restricted to fluctuations in the biaxial structure of the hybrid nematic cell with equal strengths of homeotropic and planar anchorings. The detailed analysis of the pretransitional dynamics of all five degrees of freedom around the bent-director configuration is somewhat more complicated because of the nonuniformity of the base tensors. 

Similarly, the layer compressibility constant, B, exhibits a critical variation in the vicinity of the transition. This pretransitional behavior above AN has been recognized by de Vries [32], who, by X-ray diffraction experiments, has shown the existence of small domains with a smectic... 

Pretransitional behavior of twist and splay elastic constants was also measured in CBOOA by Chu and McMillan [193]. The splay is not renormalized, whereas the twist elastic constant shows a mean-field like divergence. They also report slowing down of the twist mode near Tg, which is in apparent disagreement with both mean-field and helium-like models. A similar slowing down of the twist mode was observed by Delaye [118]. Pretransitional bend mode behavior is reported by Birecki and Litster... 

Li JL, Crandall KA, Chu P, Percec V, Petschek RG, Rosenblatt C (1996) Dendrimeric liquid crystals isotropic—nematic pretransitional behavior. Macromolecules 29 7813-7819 Lin YG, Winter HH (1991) High-temperature recrystallization and rheology of a thermotropic liquid crystalline polymer. Macromolecules 24 2877-2882 Lin Q, Yee AF (1994) Elastic modulus of in-situ composites of a liquid crystalline polymer and polycarbonate. Polym Compos 15 156-162... 

Wong, G. K. L., and Y. R. Shen. 1974. Study of pretransitional behavior of laser-field-induced molecular alignment in isotropic nematic substances. Phys. Rev. A. 10 1277 see, however, Deeg, F. W., and M. D. Payer. 1989. Analysis of complex molecular dynamics in an organic hquid by polarization selective subpicosecond transient grating experiments. Chem. Phys. 91 2269, and references therein, where the observed individual molecular reorientation effect is associated with nuclear reorientation whose dynamics is more complex than the Debye relaxation process described by Wong and Shen. 

---