Calculation of noise distribution in mesoscopic dynamics models for phase separation of multicomponent complex fluids

We present a simple method for the numerical calculation of the noise distribution in multicomponent functional Langevin models. The topic is of considerable importance, in view of the increased interest in the application of mesoscopic dynamics simulation models to phase separation of complex fluids in polymer and surfactant industries. We show that simple computational methods can be derived for a few (non)linear cases. The analysis contains three distinct steps: (I) factorization of the diffusion operator, (2) generation of auxiliary random fields and (3) Cholesky decomposition of the mobility operators.</p

Electric field versus surface alignment in confined films of a diblock copolymer melt

The dynamics of alignment of microstructure in confined films of diblock copolymer melts in the presence of an external elec. field was studied numerically. We consider in detail a sym. diblock copolymer melt, exhibiting a lamellar morphol. The method used is a dynamic mean-field d. functional method, derived from the generalized time-dependent Ginzburg-Landau theory. The time evolution of concn. variables and therefore the alignment kinetics of the morphologies are described by a set of stochastic equations of a diffusion form with Gaussian noise. We investigated the effect of an elec. field on block copolymers under the assumption that the long-range dipolar interaction induced by the fluctuations of compn. pattern is a dominant mechanism of elec.-field-induced domain alignment. The interactions with bounding electrode surfaces were taken into account as short-range interactions resulting in an addnl. term in the free energy of the sample. This term contributes only in the vicinity of the surfaces. The surfaces and the elec. field compete with each other and align the microstructure in perpendicular directions. Depending on the ratio between elec. field and interfacial interactions, parallel or perpendicular lamellar orientations were obsd. The time scale of the elec.-field-induced alignment is much larger than the time scale of the surface-induced alignment and microphase sepn. [on SciFinder (R)