2004-2005 Departmental Distinguished Seminar Series

Manoj Kumar Ram, Ph.D.

Fractal Systems Inc., Safety Harbor, Florida
January 14, 2005
Supra molecular Engineering of Conducting Materials

Rapid progress in the field of conducting polymers in the past 25 years has led to the discovery of new electronic materials, new concepts, and development of new technologies. A large number of conducting polymers such as polyacetylene, polypyrrole, polythiophene, polycarbazole, poly(phenylene vinylenes) and their copolymer, nanocomposite with metal oxide, nanocomposite with carbon nanotube etc. have been the subject of multidisciplinary research. Such conducting materials have been intensively investigated due to its excellent physical and chemical properties. Ultrathin multilayered structures of these conducting materials are important for various applications in nonlinear optics, microelectronics, light-emitting devices, and, chemical and biological sensors. The morphology and stability in electrical properties of the films are necessary for their uses in molecular electronics devices, and the sensor’s applications. An investigation of methodologies to engineer supramolecular films of organic materials was discussed. The functionalization is important for the fabrication of monolayer assembling of organic material. The Langmuir-Blodgett, layer-by-layer, insitu self-assembly techniques for fabrication of supramolecular films was presented during the talk. The physical, chemical, and structural properties of such ordered films was also discussed at length along with the chemical (NOx, NH3, CW, and BW) sensing applications of such supramolecular films. Ram’s visit was hosted by Kalliat Valsaraj.

Virginia A. Davis, Ph.D.

Rice University, Department of Chemical Engineering, Carbon Nanotechnology Laboratory
January 31, 2005
Phase Behavior Rheology, and Fiber Spinning of Single-Walled Carbon Nanotubes (SWNTs) in Superacids

In this seminar, Davis discussed her ongoing research on understanding the liquid crystal science of SWNTs and on the engineering of these suspensions into liquid crystal science of SWNTs and on the engineering of these suspensions into nanotube fibers. She also presented future directions of her research, in which knowledge of SWNT liquid crystals may be extended to other nanorods. Finally, she discussed how additional investigations of carbon nanotube structure-processing-property relationships, including the impact of nanotube length and functionalization, will facilitate the development of additional macroscopic articles including coatings and films. Davis’ visit was hosted by Douglas Harrison.

Alberto Striolo, Ph.D.

Research Associate, Vanderbilt University, Department of Chemical Engineering
February 10, 2005
Simulations: The Molecular Tool for Interpreting Experimental Results

Development in nanotechnology relies greatly on the accurate interpretation of experimental results at the molecular level. In his talk, Striolo presented two examples where molecular simulations play a major role in understanding key experimental observations. Adsorption of water in porous materials served as the first example. It has been shown that the presence of water can compromise the performance of porous carbons, widely used in the industry. Grand canonical Monte Carlo simulations are used to study water adsorption in carbon-slit pores, carbon nanotubes, and realistic representations of carbon adsorbents. The results form these simulations: adsorption isotherms, heats of adsorption, and structure of confined water. These were presented and compared to experimental data.

Complex polymeric systems containing nanoparticles, i.e. silsesquioxane monomers, served as the second example. Silsesquioxane monomers, nanoparticles based on silica and oxygen atoms, are used to reinforce polymeric materials. The mechanism of reinforcement has not yet been understood. Molecular dynamics simulations are used to characterize systems containing silsesquioxane monomers dissolved in hexadecane and poly(dymethyl siloxane). The results form these simulations: potentials of mean force and self-diffusion coefficients. These were discussed to reveal the properties of complex nano-particulate systems. Striolo’s visit was *+

Professor, Brown University, Division of Engineering-Fluid, Thermal and Chemical Processes
February 18, 2005
Nature's Minuet in C: Thermal, Catalytic, and Supramolecular Routes to New Carbon Nanomaterials
The Graffin Lecture of the American Carbon Society

Elemental carbon assembles into diverse nanoforms that include fullerenes, onions, shells, “horns,” films, and “peapods” as well as numerous nanotube and nanofiber varieties. These exciting new nanomaterials are best understood as members of the larger carbon material family that includes sorbents, fibers, composites, and structural graphites. Professor Hurt’s seminar covered the principles of carbon science relevant to both nanometric and macroscopic carbon materials. A range of new carbon nanoforms was then presented, touching on synthesis, structure, and properties, as well as selected applications and their development status. Special emphasis was given to new supramolecular routes being pursed at Brown, which are based on liquid crystal assembly and covalent capture. The talk ended with a brief discussion of the potential impacts of carbon nanomaterials on human health, and ongoing research designed to overcome this baffler to commercial success. Hurt’s visit was hosted by Judy Wornat.

Matthew Liberatore, Ph.D.

University of Delaware, Department of Chemical Engineering
February 21, 2005
Flow-induced phenomena in solutions of wormlike micelles

Surfactant molecules in solution can self-assemble into wormlike micelles. Micellar solutions are common in the cosmetic, detergent, and food industries. Solutions of these wormlike micelles have behavior similar to that of polymers, but are also able to reversibly break and recombine. Current work probing two viscoelastic micellar solutions of identical surfactant concentration has found the concentration of incorporated salt to critically influence solution behavior. While the two samples are quite similar in viscosity across a range of shear rates, only one sample exhibits shear-induced phase separation (SIPS). The important length scales of the two micellar networks are investigated via dynamic rheology, rheo-optics and small-angle neutron scattering (SANS). The smaller mesh size and entanglement length of the micelles that exhibit SIPS are smaller than the other sample. Therefore, the solution that phase separates under flow forms a more dense entangled network. Additional investigation into the nonlinear rheology of these samples finds shear banding for the sample exhibiting SIPS while the other sample behaves like a power law fluid. Based on these finds, future investigations into solutions of entangled polymers as well as surfactant-polymer mixtures appear promising, and ultimately the ability to systematically tune a material’s viscoelastic properties will be understood. Liberatore’s visit was hosted by Douglas Harrison.

George S. Goff, Ph.D.

University of Texas at Austin, Department of Chemical Engineering
March 3, 2005
Inhibiting the Oxidative Degradation of Monoethanolamine in CO₂ Capture Processes

With the increased interest in mitigating global warming, research is underway to improve existing technologies for removing CO₂ from flue gas. Aqueous absorption/stripping with alkanolamines is the current technology of choice for CO₂ capture, with aqueous monoethanolamine (MEA) being the most widely used solvent. Since most gas treating applications that use amines for CO₂ removal do not contain oxygen, oxidative degradation is an additional type of degradation specific to CO₂ removal from flue gas that can account for more than 10% of the total cost of CO₂ avoided. The current work has focused on quantifying degradation over a range of significant industrial conditions and shown that the rate of degradation is controlled by the rate of O₂ mass transfer into the amine solution. Based on this research, three additives have been identified that effectively inhibit the oxidative degradation of MEA and are currently being evaluated by a Fortune 500 engineering firm for incorporation into their CO₂ capture process. Goff’s visit was hosted by Douglas Harrison.

Jason de Joannis, Ph.D.

Postdoctoral Fellow, Emory University, Department of Chemistry
March 10, 2005
Multi-scale Modeling of Self Assembled Biological Systems Applications

Self assembled membranes provide porous encapsulation of microscopic aqueous volumes in cells and in drug delivery technologies. These bilayers are just one of the equilibrium structures formed by such amphiphilic molecules as phospholipids. Heterogeneities in the molecular distribution can give rise to special structures with stable edges such as pores or discs. The shear breadth of time and length scales arising in these systems requires that modeling efforts are directed at several levels of detail. We have used atomisitic and course-grained molecular dynamics simulations in concert with Monte Carlo techniques and with simple elastic and statistical models to further the understanding of the effect of heterogeneity on the line tension and stability of edges, and on the elasticity of a lipid bilayer. de Joannis’ visit was hosted by Douglas Harrison.

James Henry, Ph.D.

Texas A&M University, Department of Chemical Engineering
March 16, 2005
Development of Nano-Scale Sensors & Biomimetic Surfaces for Biomedical Applications

Current detection methods in biomedical applications have failed to advance at the same rate as technology. This complacency leaves a considerable void in research and development that can be filled by chemical engineers with great success. The analytical and problem-solving skills required for today’s classical chemical engineers can easily be applied to today’s biomedical and biochemical applications. Our unique analytical techniques can create a more practical point of view often overlooked by more classical scientists. This work shows how using these skills can lead to advancements in areas outside the classical bounds of chemical engineering. Examples in this work include the development of a sensor for prions (causing mad cow disease), biomimetic molecules for therapy and analysis of AB (causing Alzheimer’s disease), and a sensor for organophosphates (commonly found in neurotoxic warfare agents). Furthermore, the work addresses important characteristics and design tools that can be used in further sensor development and optimization. Henry’s visit was hosted by Douglas Harrison.

Pavel Jungwirth, Ph.D.

Research Group Head, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic
April 1, 2005
Molecular Simulations of Atmospheric Aerosols: Ions at the Air/Water Interface Applications

There is increasing evidence that the air/water interface is of a key importance in many heterogeneous chemical processes in the atmosphere, such as the release of reactive halogen species from aqueous sea salt aerosols in the marine boundary layer or tropospheric ozone destruction in the Arctic during polar sunrise. The role of aerosol loading has also been invoked in the process of thundercloud electrification. Despite this, little has been known about the structure and physical properties of aqueous aerosols at a detailed, molecular level. Here, we summarize results of molecular dynamics simulations of surfaces of concentrated aqueous salt, acid, and base solutions. The main questions addressed by the simulations concern the distribution of ions at the surface and in the aqueous bulk. A key result of the simulations is the observation that polarizable anions (e.g., chloride, bromide, and iodide), as well as hydronium cations, are present at the air-water interface of bulk solutions in amounts sufficient for the heterogeneous atmospheric chemistry to take place. The calculations also reveal that bromide and iodide actually exhibit surfactant activity, i.e. their concentration at certain regions of the interface is higher than in the bulk. This is in contradiction with the standard Onsager model of the surface of electrolytes, however, it is an accord with the observed enhanced atmospheric reactivity of aqueous bromide compared to chloride and with recent spectroscopic and SEM experiments. Jungwirth’s visit was hosted by Kalliat Valsaraj.

George “Rusty” Irwin, Ph.D.

April 15, 2005
Biotechnology and Bioprocessing: an Engineer's View

Irwin’s seminar reviewed some of the developments in biotechnology over the past 30 years as well as an analysis of the engineer’s role in this still rapidly developing technology. Specific attention was devoted to process operations and engineering skills of importance in research, development, engineering design, and manufacturing. In addition, focus on the multi-disciplinary nature of biotechnology, especially collaboration among engineers, life scientists, and regulatory agencies was discussed. Irwin is a 1974 Ph.D. graduate of our department. His visit was hosted by Kalliat Valsaraj.

Marugappan Muthukumar, Ph.D.

Professor, University of Massachusetts, Department of Polymer Science and Engineering
April 29, 2005
How DNA Worms Through Protein Channels

Professor Muthukumar’s seminar focused on the translocation of electrically charged macromolecules through narrow channels as a fundamental process in life. The physical chemistry of this process was narrated using simulations and polymer physics concepts against a background of single-molecule experiments. Specifically, the movement of single-stranded DNA/RNA through alpha- hemolysin channels under an external electric field was exemplified. The implications to DNA-sequencing in biotechnology, and transport of mRNA through nuclear pores in mammalian cells was also discussed. Muthukumar’s visit was co-hosted by Paul Russo (LSU Department of Chemistry) and Karsten Thompson.