Ionization and Conformation Consistency in Weak Polyelectrolytes Near Interfaces

In contrast to strong polyelectrolytes, weak polyelectrolytes present electrostatic charges in accordance with the solution pH and the local chemical environment. The pH-responsive behavior is advantageous for applications in smart systems to achieve specific functions such as targeted drug delivery and controlled release. Unfortunately, a quantitative description of such behavior remains challenging. In an inhomogeneous fluid such as near an interface, these important inter- and intrachain correlations effect play a key role in the interfacial behavior which is not accounted for in current theoretical approaches. By coupling a molecular thermodynamic model for chemical reactions with the polymer density functional theory (DFT), we can incorporate these correlation effects to describe the interfacial behavior of weak polyelectrolytes in good agreement with experimental data. We demonstrate that the long-range two-body intrachain correlations can be incorporated into the so-called single-chain-in-DFT simulation to accurately capture the self-consistency between ionization and conformation in weak polyelectrolytes.