Surface Morphologies of Polyzwitterionic Brushes Induced by Electrostatic Strength and Counterion Valence

The surface phase behavior of planar polyzwitterionic brushes was studied by molecular dynamics simulations. The evolution of the surface morphologies of polyzwitterionic brushes with the strength of electrostatic interaction in the presence of counterions with different valences was investigated. When the electrostatic interaction was gradually enhanced,the microphase separation of the polyzwitterionic brush occurred in all three cases to form a pinned micelle structure. Combining brush height,density distribution function,and backbone monomer pair correla. tion functions,the changes of micelle size and particle stacking state in micelles were analyzed. The difference between monovalent and multivalent counterions in inducing the phase structure of polyzwitterionic brushes was revealed by calculating the fractions of four states of positive counterions in the brushes.