Adsorption of Charged Polymers

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

0102267 Rubinstein This award supports theoretical and computational research on charged polymer adsorption at surfaces and interfaces. Research will focus on hydrophilic and hydrophobic polyelectrolytes. The PI will develop an analytical model of adsorption of hydrophilic polyelectrolytes in the presence of short-range and long-range interactions between polymers and surfaces. De Gennes' self-similar carpet model of short-range adsorption of uncharged polymers will be combined with a model of long-range adsorption of polyelectrolytes to oppositely charged surfaces. Another model will be developed to study hydrophobic polyelectrolyte adsorption in the presence of both short-range and long-range interactions. The properties of hydrophobic polyelectrolytes in solution will be studied in more detail to enable the extension of adsorption models to hydrophobic polyelectrolytes. The interplay of short-range attraction and long-range (electrostatic) repulsion leads to a necklace conformation of hydrophobic polyelectrolytes. Computer simulations and scattering experiments have recently confirmed the main features of the necklace model of hydrophobic polyelectrolytes. The remaining open questions important for the application of the model to the adsorption of hydrophobic polyelectrolytes will be investigated using a combination of analytical calculations and computer simulations. The resulting model of hydrophobic polyelectrolyte solutions will be combined with the adsorption model of hydrophilic polyelectrolytes into an adsorption model of hydrophobic polyelectrolytes. The kinetic theory of polyelectrolyte adsorption at charged surfaces will be developed using de Gennes' two-step approach in the framework of Rouze-Zimm model for unentangled adsorbed layers and of tube models for entangled layers. A wide range of educational activities spanning K-12 outreach to the education of postdoctoral research associates are supported by this grant. This award also provides partial support of the preparation of a polymer physics textbook. %%% This award supports theoretical and computational research that contributes toward the development of a complete molecular picture of the adsorption of charged polymers on charged surfaces. Adsorption of charged polymers is one of the least understood areas of polymer physics. The technological importance of charged polymers as rheology modifiers, dispersing aids, stabilizers, and binders is due to their unique properties both in solutions and near surfaces. An application in the area of nanoscale science and engineering is multilayer formation via layer-by-layer deposition of oppositely charged polyelectrolytes, leading to novel methods of nanodevice fabrication. A better understanding of charged polymers will also impact molecular biophysics because many biopolymers, such as DNA and proteins, are charged, and electrostatics plays a significant role in their properties and function. The award will also support a wide range of educational activities including K-12 outreach and education in polymer physics and chemistry at the undergraduate, graduate, and postdoctoral levels. Some of the research will be included in the Polymer Physical Chemistry course sequence at UNC and in a textbook that is in preparation. ***