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Complex Materials Group

Complex Materials Group. Peter F. Green Department of Chemical Engineering and Texas Materials Institute The University of Texas at Austin. Motivation for research : problems at the nanoscale in polymer based systems. Conventional applications: Coatings Membranes Lubrication

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Complex Materials Group

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  1. Complex Materials Group Peter F. Green Department of Chemical Engineering and Texas Materials Institute The University of Texas at Austin

  2. Motivation for research : problems at the nanoscale in polymer based systems • Conventional applications: • Coatings • Membranes • Lubrication • Processing: • Self assembly • Lithography • Device technologies • Light emitting diodes • Organic photodiodes • Sensors h~1-50 nm Particles of Nanoscale dimensions Polymer is the active material component thin film transistor (T. Kawase, et. al. Digest of Technical Papers 2001)

  3. Disordered Ordered Polymer thin films (h~1-100 nm) exhibit properties that differ from the bulk (new phenomena) • Confinement (entropic), enthalpic (polymer-polymer) interactions and interfacial interactions influence properties • Surface induced ordering of block copolymers • phase stability (change in Tc) • Dynamics (Viscosity, chain diffusion) • Glass transition temperature Tg • Instabilities and pattern formation

  4. Topics of Interest: Self-Organization, Dynamics and Wetting • Polymer-nanoparticle systems (bulk and thin film) • Glass Transition temperature of thin films • Chain dynamics and miscibility in confined geometries • Instabilities in thin films (mixtures and homopolymers) • Wetting and nano-scale organization of structured liquids • Polymer thin film/CO2 systems (with Johnston group)

  5. Polymer-based Nanocomposites • Properties at the nanoscale are of broad interest, cross-cutting many disciplines… diverse technical issues (e- transport and single-molecule transistors to mechanical properties and automobile bumpers) • Polymer-based nanocomposites: polymers+ nanoscale particles (fullerenes, layered silicates, nanoparticles, nanotubes)-new pathways to “tailor” properties of materials Thin film 20-50 nm Polymer coil Rg~2-20 nm

  6. h1 h2 h3 L Self Organization of chains on a surface determined by film thickness, temperature, substrate topography Effects of temperature and film thickness

  7. Patterned Substrates

  8. The Glass transition temperature of nanocomposite thin films • Background: The glass transition temperature of polymer thin films • Influence of • i) single walled carbon nanotubes, • (ii) C60 fullerenes (“buckyballs”) and • (iii) mica-type layered silicate inorganic clays • on the Tg of thin polymer films in the nanometer thickness range from mmptdpublic.jsc.nasa.gov/jscnano/ 20-50 nm Polymer coil Rg~2-20 nm

  9. The Glass transition of Polymer thin film nanocomposites • C60, and carbon nanotubes have a similar effect PS: b=9 Nanocomposite: b=4 Decrease in b reflects the increase in fraction of the slowly relaxing domains The effect of nanoparticles is to increase the effective fraction of slowly relaxing domains in the sample

  10. Phase Separation Glass Transition Dynamic processes in confined environmentsNeutron scattering experiments Relaxation processes affect scattering intensity as well as change d <u2>/dt Reduced Intensity Temperature (K)

  11. Dewetting of Thin Films film • Mechanisms (determined by the nature of the intermolecular interactions) Nucleation: Heterogeneous and homogeneous Spinodal Dewetting: Spontaneous amplification of capillary waves Droplets substrate

  12. Misc. Info about the group • Current Funding: National Science Foundation (DMR, STC), Robert A. Welch Foundation, Sematech • Facilities used: Atomic force microscopy, spectroscopic ellipsometry, X-ray Scattering, TEM, neutron scattering, dynamic mechanical analysis, rheology • Collaborations: Johnston, Ganesan, Sanchez, Yacaman Loo, Bonnecaze, Korgel • Distribution of Researchers during last 12 months: 9 PhD Students (2 co-advised), visiting scientist, undergraduates, shared post-doc (Johnston group)

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