Theory of the structure of adsorbed block copolymers: Detailed comparison with experiment

Abstract

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.

The influence of grafted polymer architecture and fluid hydrodynamics on protein separation by entropic interaction chromatography

“…In the absence of flow, fðrÞ shows a maximum as r decreases away from the grafting surface at r ¼ r wall , followed by a region of decreasing density that terminates in a smooth tail region. This predicted density profile closely matches those measured by atomic force microscopy and neutron scattering experiments for polymer brushes grafted to planar surfaces (Baranowski and Whitmore, 1995;Cosgrove and Ryan, 1990;Field et al, 1992;Guffond et al, 1997), with the exception that our model predicts that grafting inside a cylindrical pore slightly compresses the extended tail region of the brush due to the decreasing solvent volume available to the chains as r approaches zero.…”

End‐Anchored Polymers: Compression by Different Mechanisms and Interpenetration of Apposing Layers

“…It also allows for a depletion layer, with a width that is independent of N but varies as S 1/2 . A number of early experiments were originally interpreted as agreeing with these predictions, in particular that the layer thickness scales linearly with N. However, a subsequent analysis [24] of the same experiments indicated otherwise, with significantly weaker scaling. There have been other differences as well.…”

“…In previous work, our group has used NSCF theory to model end-anchored polymers in good, Y, and poor solvents. [23][24][25] In some cases, we used experimentally-determined values for the statistical segment lengths as well as pure monomer and solvent densities, and we were able to make detailed, quantitative comparison with experiments. For uncompressed layers, the density profiles agreed well with the ones observed by Kent et al, except for the plateaus in the case of the Y solvents.…”

Steric Stabilization of Colloids by Poly(dimethylsiloxane) in Carbon Dioxide: Effect of Cosolvents

“…If this is the case, even at pressures above the UCSP, the system will flocculate. The graft density for the 10K and the 22K PDMS indicates that the polymers have a high reduced coverage, σ * > 6 (35). At this high coverage, interactions with the silica surface can be ignored (36).…”