ABSTRACT CTS-9817048 Santore, Maria/Lehigh U. This program targets the generation of rules for the custom design of polymeric additives that will bring several industrial sectors closer to environmental compatibility: coatings formulation (replacement of organic formulations with aqueous ones), waste water treatment (flocculants effective for aggressively aerated low solids sludges), paper making (increased white water recycle and lower waste stream volume), aqueous lubrication, and oil recovery (biodegradable additives compatible with sandstone formations). In these instances environmental compatibilization depends on a fundamental understanding of the transient dynamic aspects of polymer adsorption and colloidal phenomena. In particular, the program targets the questions of how specific polymer chemistry and architecture determine (1) adsorption rates and (2) interfacial relaxations. The program then addresses (3) how adsorbed layers in different stages of relaxation mediate colloidal interactions and cause stabilization or flocculation. The outcome from this program, in addition to design rules that allow one to tailor molecules that are dynamically responsive to the timescales of particular processes, includes information about transient colloidal potentials that will facilitate process-specific flocculation and stabilization models. The core scientific program at Lehigh is supplemented with liaison projects involving 4 companies, coop programs, and 5th year masters programs, for the most effective technology transfer to bring the fundamentals to the specific industrial situations. An experimental program employing model narrow molecular standard water soluble polymers (polyethylene oxide and pullulan - based) and substrates of controlled chemistry (through the deposition of self assembled monolayers) will allow systematic variations in the relevant chemical and architectural parameters in studies of adsorption, interfacial relaxation, and the evolution interfacial colloidal for ces. Use of these model systems is critical to the development of theory for dynamic behavior. The issues of adsorption, relaxation, and colloidal forces will be probed through a unique combination of techniques. Polymer adsorption and relaxation kinetics will be measured with a synergistic combination of total internal reflectance fluorescence (TIRF) and near-Brewster reflectivity, developed in the PI's lab under prior NSF support. Together the two methods measure the evolving surface mass, the evolving layer thickness and density, and the kinetic behavior of fluorescently-tagged interfacial populations. Interfacial relaxations will be further probed through self exchange studies using TIRF. These studies will establish the evolutionary timescales of the layers and provide some idea of which layer features evolve. Models developed under a Research Initiation Award will be modified to give quantitative explanation of the observed dynamics. The next phase of work relates this evolving layer structure to colloidal behavior. Dynamic measurements of colloidal forces will be measured using 'MASIF," similar to the surface forces apparatus, but designed for dynamic data acquisition. Finally impinging jet colloidal deposition studies will be employed to measure how interfacial relaxations and pairwise colloidal force measurements translate to flocculation or stabilization in situations of strong shear and hydrodynamic collision forces. The sticking ability, as a function of the transient interfacial state and hydrodynamic conditions can be used in existing flocculation models to make them more process-specific for wastewater, paper, coatings, and oil recovery applications.
