Solvation Studies of Responsive Polymers in Solution and at Surfaces

Texas A&M Research Foundation, College Station TX

Investigators

Abstract

ARRA STATEMENT: This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). TECHNICAL SUMMARY: This proposal will examine the effect of polymer microstructure, solvent additives and solution components on lower critical solution temperature (LCST) phenomena both in solution and at surfaces. The studies proposed will use solution state light scattering analyses of cloud point behavior mostly using a bulk phase microanalytical automated digital melting point apparatus to study small scale samples in parallel. Other analytical techniques will be employed too. For example, fluorescence spectroscopy with labeled polymers will probe polymer aggregation events that occur before and after visible phase separation starts and ends. The effects of small molecule and macromolecular co-solutes on LCSTs of a variety of polymers with structurally isomeric repeating units will be carried out to determine how ionic, covalent and macromolecular co-solutes affect a given polymer's LCST. The structural and chemical information generated in these solution-state studies will then be used to develop new sorts of stimuli-responsive surfaces that reversibly change between being superhydrophobic or hydrophilic. Such surfaces physical properties will also be studied to determine if the hydration changes of the polymer grafts alter surface mechanical properties such as viscoelasticty and adhesion. These surfaces with be studied using a battery of analytical methods. The surface structural changes associated with reorganization of these surfaces that will be in the form of thin film nanocomposites in response to solutes in bulk water component will be followed, and, in suitable cases, will be monitored in real time. NON-TECHNICAL SUMMARY: This proposed work will study the molecular details of stimuli-responsive macromolecular solubility. This will primarily involve studies of how a macromolecule's temperature-dependent solubility changes in response to the presence of other species in solution. These studies will include studies of aqueous polymer solutions and studies of polymer-containing coatings on solid surfaces. Such responsive polymer solubility studies are important because such materials are components of responsive catalysts and sensors. Polymer solubility and the temperature dependence of polymer solubility is also critically important in determining the stability and activity of proteins and enzymes. Extending studies of solution behavior of macromolecules to include surfaces will lead to a better understanding of responsive wettability of surfaces and the design of 'smart' surfaces. Such 'smart' surfaces have potential as new materials that are self cleaning, that have controllable adhesion, or that have varied surface friction. These studies will have broader impacts that include both undergraduate and graduate education in the research laboratory and classroom. Extramural dissemination of results in presentations to audiences in industry, at predominantly undergraduate institutions, and at international venues will publicize the results of these studies. The chemical methodology used in this research will be developed into experiments that will be used in freshman chemistry courses to educate students about the consequences of enthalpy and entropy in macromolecule hydration. International research collaborations will be fostered and will involve programs with groups in Europe, China, and Qatar.