GOALI: Generation, Characterization, and Modeling of Structure and Properties of Polymer Blend Nano- and Microparticles

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9982077OtaigbeThis GOALI award, jointly supported by the Div. of Materials Research and the Office of Multidisciplinary Activities of the Directorate for Mathematical and Physical Sciences, is in the area of nanoscience. New dynamic behavior emerges when polymers are confined in a small droplet of solution the size of a molecule or in molecular aggregates. Solvent evaporation takes place on a time scale short enough to frustrate phase separation, producing dry pure polymer or polymer blend microparticles that are homogeneous within molecular dimensions. This capability allows production of spherical polymer alloy microparticles with tunable properties (such as refractive index) simply by adjusting the relative weight fractions of the polymers in solution. This research will develop a methodology for generating polymer and polymer blend microparticles and for probing the structure, morphology, and other characteristics of the polymer micro- and nanoparticles. Using instrumentation developed for probing single fluorescent molecules in submicrometer droplets, the proposal will demonstrate that polymer particles of nearly arbitrary size and composition can be made with narrow size dispersion. While the focus of this research is on polymeric systems, the microparticle generator can be easily adapted to make small organic and inorganic particles (and hybrid systems). A number of optical methodologies such as Fraunhofer diffraction, fluorescence, and conventional phase-contrast microscopy will be used to probe polymer particles immobilized on two-dimensional subrstrates or levitated in space using a three-dimensional quadrupole (Paul) trap. The optical diffraction method will provide a unique look (not possible now with conventional methods such as electron-beam microscopy) inside a polymer particle in a measurement time schale of a few milliseconds, making it attractive to in-line production applications.The knowledge gained will be useful in addressing phase separation, the primary barrier to producing many technologically relevant and scientifically interesting homogeneous polymer blends from bulk-immiscible components in solution. Examples of application areas of the polymer microparticles include polymer blends or alloys, biomaterials for drug delivery systems, electro-optic and luminescent devices, polymer powder spray coating, and polymer powder impregnation of inorganic fibers in composites and in polymer-supported heterogeneous catalysis.