Exploration of Polyelectrolyte Film Properties Relevant to Membrane-based Separations and Sample Introduction

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Professor Merlin Bruening of Michigan State University is supported by the Analytical and Surface Chemistry Program to synthesize and evaluate the performance of ultrathin polyelectrolyte films in order to develop high-flux, selective membrane skins. The initial objective is to make polyimide films by alternating adsorption of poly(amic acids) (PAA) and poly(allylamine hydrochloride) and subsequent imidization. An aim is to determine the minimal thickness at which the polyimide film can still exhibit selectivity and permeability. The second goal is to develop methods of adsorption of these skins onto practical supports that contain large or ill-defined pores. The work will involve synthesis of highly branched polyelectrolyte gutter layers that have very large permeabilities. AFM images, transport measurements and infrared spectra will be used in their characterization. A second section of the work aims at creating high-flux membranes that quickly and selectively remove organics from water. Such membranes will be tested in membrane induction mass spectrometry (MIMS). A third area deals with using derivitized PAA films to preconcentrate and filter proteins and DNA prior to analysis by matrix-assisted laser-desorption/ionization mass spectrometry (MALDI-MS).Chemical analysis of mixtures often requires a pre-treatment step in order to simplify the sample, lowering concentrations of interferents. Membranes offer potential in this regard, and could be used for rapid and sensitive analysis of aqueous pollutants or chemical warfare agents. This research on new growth methods of membranes and new membrane materials will advance our understanding of this potentially inexpensive and environmentally clean way to expedite chemical analysis. Another application of the project is in mass spectrometry of the proteome.