Dr. Priestley came to speak to the students at Lafayette College on April 9th 2014 on his research in the field of:
“Polymer Nanoparticles: Confinement Effects and Novel Processing”
In this talk, we discuss two important themes in contemporary polymer science: nanoscale confinement effects on polymer properties and new routes of processing nanomaterials, i.e., nanoparticles. Concerning the former, significant effort has been devoted to pursing an understanding of the glass transition temperature of polymers confined to the nanoscale. Much of our understanding has been obtained via studies on thin polymer films. Here, we show the glass transition temperature of polymer nanoparticles can deviate significantly from the bulk value. Our work suggests a common origin of size effects of the glassy properties of confined polymers, irrespective of geometry, that is, interfacial effects. We also discuss the influence of surfactants and the dispersing media on the glass transition temperature and fragility of polymer nanoparticles. With regards to the later theme, aside from polymerization techniques, polymer nano- particles can be generated through the displacement of a solvent with a nonsolvent, i.e., nanoprecipitation. Here, we pre- sent a facile process termed Flash NanoPrecipitation (FNP) to generate homogeneous and heterogeneous polymer nano- particles. As compared to polymer nanoparticles synthesized by surfactant free emulsion polymerization, nanoparticles prepared by FNP show comparable size distributions when the diameter is less than 150 nm. Furthermore, we illustrate that the sizes of polymer nanoparticles prepared by FNP can be fine-tuned by changing the polymer and/or electrolyte concentration. Calculations of the mechanism of particle formation and stabilization show that the size-dependent electrostatic repulsions between nanoparticles and nanoparticles versus single collapsed polymer chains control assembly and monodispersity. We also discuss recent developments of the FNP process to form polymer-polymer Janus nanopar- ticles and metal-polymer supported nanoparticles. Lastly, we discuss a one-step polymerization based approach to form nanostructured templates to create yolk-shell nanoparticles.
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