Optical micrographs showing the phase separation of the 8CB/PS blend (70/30 wt %) during the quench/jump process. (a) Morphology after quench from isotropic (I) region (60^{o}C) isotropic - isotropic region (I + I) at temperature 41^{o}C after 18 h of phase separation., (b-f) time evolution of the phase separation proves after second quench to nematic - isotropic (N + I+ region (39^{o}C) in the (b) t = 2 min, (c) t = 3 min, (d) t = 6 min, (e) t = 9 min, and (f) t = 20 min, t is the time spent after the second quench. These micrographs are obtained from the same area. Micrographs (b-f) show how fast the isotropic domains surrounded by the anisotropic phase (nematic) merge. The size bar of 10 um is the same for all micrographs. In the isotropic phase, the domains stayed close together for hours without coalescence, while in the nematic phase the same domains merge in short time of minutes. Therefore, we suppose that there must be an attractive force in the nematic which pulls the domains together. (M. Graca, S. A. Wieczorek, and R. Holyst Macromolecules 2003, 36, 6903-691) |