Spinodal decomposition in a semidilute suspension of rodlike macromolecules - art. no. 011501

The Doi-Shimada-Okano [J. Chem. Phys. 88, 4070 (1988)] theory of the spinod al decomposition in a suspension of rods is reinvestigated analytically. Sh ort enough rods may rotate fairly unhindered so we emphasize translational diffusion. The excluded-volume effect between the rods gives rise to a coup ling of the orientational and translational degrees of freedom. This effect may be addressed correctly because the kernel in the equation describing t he dynamic evolution of the one-particle distribution turns out to be degen erate. The two principal eigenvalues calculated analytically agree with pre vious numerical work by Maeda [Macromolecules 22, 1881 (1989); 23, 1464 (19 90)]. It is concluded that the associated relaxation modes do not represent pure density and orientation fluctuation modes.