Simulations Of Polyelectrolyte Brushes Grafted On Three Surfaces

Using molecular dynamics simulation,the effects of the grafting density and the charge fraction on the conformation on hexahedral,pentahedral and tetrahedral polyelectrolyte brushes are investigated.With the increase of the grafting density,the hexahedral brush firstly condensed under the effect of trivalent counterions,followed by the pentahedral brush,while the tetrahedral brush was least prone to condense;For the high charge fraction(f = 1.0),the hexahedral(pentahedral,tetrahedral)polyelectrolyte brushes collapsed rapidly on the trivalent counter-ion,and patches formed on the grafting surface.With the increase of grafting density,the number of patches showed a declined trend.In addition,when the number of patches was greater than two,the positions of the patches located nearly the sides or corners,indicating that the patches are preferred in places where the curvature is large;For hexahedral(pentahedral,tetrahedral)polyelectrolyte brushes,both the monomer-monomer and monomer-counterion correlations increased with the charge fraction and grafting density.In the investigation of the conformations of pentahedral(tetrahedral)polyelectrolyte brushes with the charge fraction,it was found that the condensed of trivalent ions dominates when the charge fraction f was less than 0.67.As the charge fraction increases,the polyelectrolyte chains aggregated and collapsed,and the average brush height quickly reduced.