The work to be conducted under this award is to examine phase behavior of solutions of synthetic polyelectrolyte complexes and to then use an electric field to manipulate these complexes in solution with the goal of depositing them as solids onto substrates. Synthetic polyelectrolytes, both strong and weak, that are typically used in layer-by-layer (LbL) assembly of polyelectrolyte multilayers (such as polyacrylic acid, sulfonated polystyrene, polyallylamine hydrochloride, and polyethylene imine) will be examined. The first part of the work will be to determine phase diagrams for the complexes of different pairs of polyelectrolytes as a function of pH, solution ionic strength, molecular weight, and concentration. The thermodynamic behavior of these complexes is generally masked by kinetic considerations, and unraveling these components will be one goal. The next phase of the work will be to look at adsorption of complexes of different stoichiometries onto charged surfaces. The third phase of the work will be to compare this equilibrium adsorption to deposition onto charged surfaces under the influence of an electric field. Factors including ionic strength, dielectric constant of the solvent, and addition of other components such as metal nanoparticles will be examined. This process will eventually be generalized to look at the electrophoretic deposition of other types of soft matter such as micelles or hollow polyelectrolyte capsules. The last phase of the work is to examine the solid materials created by this process. It is hypothesized that different stoichiometries and properties can be achieved through electric field manipulation as compared to equilibrium adsorption onto a surface.
NON-TECHNICAL SUMMARY:
Polyelectrolytes (PEs) can be compared very long molecular salts, i.e. long-chain molecules made up of a sequence of either positive or negative charges. They tend to be water-soluble and are often used in pharmaceutical, cosmetic, or food formulations. Biological materials such as proteins and DNA are examples of polyelectrolytes. PEs can be processed into thin coatings with a range of very useful properties by a technique of sequential adsorption steps. These coatings have possible applications in alternative energy devices, biomedical devices, energy saving coatings for windows, and any number of other possibilities. One major barrier to their commercialization is the long time required to make these coatings. The work proposed here is to look at electric fields as a tool to enhance the deposition times for coatings made of polyelectrolytes. This potential has the impact to make these materials commercially viable. This work will help to train PhD students as well as undergraduate students, to engage them in science. Outreach will be done with community college students who are considering transferring into four-year programs. Special attention will be paid to the mentoring of undergraduate and graduate students from under-represented groups, especially female students and those students who are the first in their family to attend college. The PI already has a strong record of working with students from these groups.
