Orientation fluctuation-induced spinodal decomposition in polymer-liquid-crystal mixtures

We study the early stages of spinodal decomposition (SD) in polymer-liquid- crystal mixtures by solving linearized time-dependent Landau-Ginzburg equat ions for concentration (conserved order parameter) and orientation (noncons erved order parameter). The theory takes into account a cross term between concentration and orientation gradients, which becomes an important factor for phase separation kinetics. We calculate structure factors for concentra tion and for orientation, depending on a quench temperature and concentrati on. We find a new SD process driven by instability of the orientational ord er parameter. In this case, the average domain size initially grows as a no ntrivial and evolving power of time, which starts as t(1/3) in our minimal model. The domain growth is advanced by the coupling between the two order parameters.