Spinodal decomposition of a rigid-rod system
Micah J.
Green, Robert C. Armstrong, Robert A. Brown
Department of Chemical Engineering, 66-258
Massachusetts Institute of Technology
The spinodal decomposition of rodlike particles is simulated for a one-dimensional system with both periodic boundaries and hard wall boundaries. The nonhomogeneous Doi equation for the rod distribution function is discretized by the finite element method and integrated forward in time using a parallel, semi-implicit scheme. The simulation uses a discretized form of the full nonhomogeneous Onsager intermolecular potential which models interactions of the rods on the scale of a single rod length. This intermolecular potential makes it possible to characterize nonhomogeneous structures and interfaces in terms of the rod length with no adjustable parameters. The method is applied to isotropic-nematic spinodal decomposition and to the behavior of misaligned nematic grains. The effects of rotational and translational diffusivity ratios are computed, and the mechanisms for alignment and phase separation are analyzed. These results mark the first full computation of the distribution functions evolution for spinodal decomposition in nonhomogeneous rigid-rod systems.