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Soft Matter

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Soft Matter, 2009, 5, 413 - 424, DOI: 10.1039/b809095e

Internal structure and charge compensation of polyelectrolyte multilayers: a numerical study

Qiang Wang

Using a self-consistent field theory, we have modeled the sequential process of layer-by-layer (LbL) assembly of flexible polyelectrolytes (PE) on flat substrates as a series of kinetically trapped states. Up to 60 alternating depositions of polyanions and polycations are performed, each followed by a washing step. We have studied the internal structure and charge compensation of PEM formed by both strongly and weakly dissociating PE, and the effects of various parameters affecting the long-range electrostatic interactions (including the substrate charge density, polymer charge fractions, bulk salt concentrations) and short-range interactions (including the solvent qualities and repulsion between polymers) in the system. Our modeling of PE LbL assembly is in good qualitative agreement with most experiments and molecular dynamics simulations. Many of our results can also be quantitatively tested in experiments. Finally, we do not find multilayering in the equilibrium adsorption of PE mixtures from a bulk solution containing both the polyanions and polycations, indicating that LbL assembly is a non-equilibrium process.

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