Modeling Layer-by-Layer Assembly of
Flexible Polyelectrolytes
Qiang Wang
Department of Chemical and
Using a continuum self-consistent field theory, we have modelled
the sequential process of layer-by-layer assembly of flexible polyelectrolytes on
flat surfaces as a series of kinetically trapped states. Up to 60 depositions
of oppositely charged polyelectrolytes are performed, each followed by a
washing step. The multilayer has a three-zone structure. An exponential growth
is found for the first several layers, followed by a linear growth for
subsequent layers evolving towards a steady state. Each layer inverts the total
charge of the multilayer film (including the bare substrate charge). While
adjacent layers are highly interpenetrating, stratification can be seen for
every four or more layers. We have also examined the effects of surface charge
density, bulk salt concentration, and solvent quality on the thickness and
internal structure of the multilayer. Our results agree with most experimental
findings on polyelectrolyte layer-by-layer assembly.