Articles you may be interested inMicelle shape transitions in block copolymer/homopolymer blends: Comparison of self-consistent field theory with experiment We present a numerical, self-consistent field study of adsorbed diblock copolymers in thermal solvents, with a detailed and quantitative comparison with recent experiments performed on poly͑dimethylsiloxane-block-styrene͒ copolymer spread as a monolayer at the free surface of ethyl benzoate ͓M. These neutron reflectivity experiments, for the first time, independently varied both the molecular weight and surface density, and probed the size and nature of the depletion layer at the surface. In the calculations, the polymer and solvent are characterized by realistic values of the pure component densities, the Kuhn length and the Flory interaction parameter. We examine the properties of the dangling block, specifically the depletion layer, the thickness of the brush, the maximum polymer concentration and its location, and the dependence of these properties on surface density and molecular weight. We obtain very good agreement with the experiments, especially for the functional dependences, which indicate that these systems are not in the asymptotic brush limit. We also argue that this conclusion applies to many experiments, some of which were previously thought to be in the asymptotic limit.

Summary: This paper presents a systematic study of the compression of end‐anchored polymer layers by a variety of mechanisms. We treat layers in both good and Θ solvents, and in the range of polymer densities that is normally encountered in experiments. Our primary technique is numerical self‐consistent field (NSCF) theory. We compare the NSCF results for the different mechanisms with each other, and with those of the analytic SCF theory. For each mechanism, we calculate the density profiles, layer thicknesses, and free energies, all as functions of the degree of polymerization and surface coverage. The free energy and the deformation of each layer depend on the compression mechanism, and they can be very different from the ASCF theory. For example, the energy of compression can be as much as three times greater than the analytical SCF (ASCF) prediction, and it does not reduce to simple, universal functions of the reduced distance between the surfaces. The overall physical picture simplifies if the free energy is expressed in terms of the layer deformation, rather than the reduced surface separation. We also examine and quantify the interpenetration of layers, discuss why ASCF theory applies better to some compression mechanisms than others, and end with comments on the difficulties in extracting quantitative information from surface‐forces experiments.Comparisons of forces of compression in a good solvent for the three different systems, as functions of D/nb. The lower three curves are for σ* = 3, and the upper three are for σ* = 23.imageComparisons of forces of compression in a good solvent for the three different systems, as functions of D/nb. The lower three curves are for σ* = 3, and the upper three are for σ* = 23.

We present a numerical, self-consistent field (SCF) study of tethered polymers in Θ solvent, over the range of anchoring densities found in most experiments. We examine the properties of the dangling block, including the thickness of the brush, the density profile, the depletion layer, the maximum polymer concentration and its location, and the dependence of these properties on surface density and molecular weight. In the calculations, the polymer and solvent are characterized by realistic values of the pure component densities, the statistical segment length, and the Flory interaction parameter, and we make quantitative comparison with recent experiments [M. S. Kent, G. S. Smith, J. Majewski, L. T. Lee, and S. Satija, J. Chem. Phys. 108, 5635 (1998)] and with the asymptotic analytic SCF theory. In agreement with these experiments, our results add to the growing body of evidence that many of these systems are not well described by the asymptotic theories.