Gaussian ellipsoid model for confined polymer systems

Abstract

Polymer systems in slab geometries are studied on the basis of the recently presented Gaussian Ellipsoid Model [J. Chem. Phys. 114, 7655 (2001)].The potential of the confining walls has an exponential shape. For homogeneous systems in thermodynamic equilibrium we discuss density, orientation and deformation profiles of the polymers close to the walls. For strongly segregated mixtures of polymer components A and B equilibrium profiles are studied near a planar interface separating A and B rich regions. Spinodal decomposition processes of the mixtures in the presence of neutral walls show upon strong confinement an increase of the lateral size of A and B rich domains and a slowing down of the demixing kinetics. These findings are in agreement with predictions from time dependent Ginzburg--Landau theory. In the case, where one wall periodically favors one of the two mixture components over the other, different equilibrium structures emerge and lead to different kinetic pathways of spinodal decomposition processes in such systems.Comment: 18 pages, 16 figures, submitted to J. Chem. Phy

Theory and Simulation of Multiphase Polymer Systems

“…If details of the conformations are not of interest, the polymers can be replaced by single, soft particles with ellipsoidal shape. The idea was then pursued mainly by Eurich, Maass, and coworkers [217][218][219], who also suggested to extend the model to diblock copolymers by modeling them as dimers to account for their dumbbell shape [219]. Sambrisky and Guenza have recently worked out a microscopic foundation for coarse-graining diblock copolymers into such dumbbells, which is based on liquid-state integral equations [220].…”

Soft particle model for block copolymers

“…As a test of (9) we compare with Monte Carlo simulations the conditional probability W (r|R A ) obtained from ( 9) by integrating over the orientations of r with r = | r| fixed, and by averaging over R B . Regarding its dependence on R A , we took averages over each of eight successive intervals on the R A axis chosen such that they have equal weights 1/8 with respect to the distribution (7). Results are shown in Fig.…”

“…We start with planar walls parallel to the (x, y)-plane, with a potential for A and B monomers as in Ref. 7 ,…”

“…In a subsequent extension to confined systems it was shown how spinodal decomposition in polymer blends becomes modified in thin films, including situations of periodically patterned walls. 7 Soft particle models become increasingly valuable in the description of complex matter systems, and also analytical techniques can be used to relate the input parameters to microscopic properties. 8,9 In this paper we propose a soft particle model for block copolymers.…”

“…Motivated by the results of Refs. 6,7 we explore the possibility to map the internal molecular degrees of freedom onto only a few parameters, allowing straightforward physical interpretation. In other words, we attempt to coarse-grain as far as possible while keeping the most important structural characteristics of individual molecules.…”