(2fy) Ionization and Conformation Consistency in Weak Polyelectrolytes Near Interfaces

Charge regulation, Interfacial behavior of polymers, Bioadhesives, Energy Storage

Teaching Interests:

Statistical Thermodynamics, Polymer Physics, Computational Methods

Abstract:

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. While in recent decades, there has been significant progress to describe weak polyelectrolytes in the bulk and near an interface, these studies neglect explicit consideration of both the inter- and intrachain electrostatic correlations important for the interactions of weak polyelectrolytes in solution. As a result, they are unable to predict the influence that changes in solution conditions (e.g. salt concentration) has on the bulk titration behavior of weak polyelectrolytes. Furthermore, in an inhomogeneous fluid such as near an interface, these important 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 correlation effects into the conventional models and describe the interfacial behavior of weak polyelectrolytes in good agreement with experimental data. A major challenge is the inclusion of long-range two-body intrachain interactions between charged sites in the polymer chain, particularly in an inhomogeneous fluid. We demonstrate that such effects can be conveniently incorporated into the so-called single-chain-in-DFT simulation (an improvement upon the conventional single-chain-in-mean-field simulation) to accurately capture the self-consistency between ionization and conformation in weak polyelectrolytes.