Research In The DeSimone Lab

Our research group examines all aspects of polymer synthesis and processing, from fundamental aspects of chemical systems to the most effective and environmentally friendly ways to manufacture polymers and polymer-based products and devices. We accomplish our highly diverse research goals by drawing on the expertise of the world class faculty of both NC State University's Chemical Engineering Department and the Department of Chemistry at the University of North Carolina at Chapel Hill. Additionally, our students enjoy extensive collaborations with researchers at numerous national laboratories and in private industry. Students in our group have at their disposal a broad range of state-of-the-art analytical techniques including: high pressure spectroscopic methods, multi-nuclear NMR, thermal analysis, GPC, dynamic and static light scattering, and neutron and X-ray scattering methods.

Synthesis of New Polymeric Materials:
Our group is heavily focused on the successful design of new polymeric materials that have the requisite properties to be effective in particular applications. Some specific examples are listed below.

Microfluidics: One of our projects involves the design of multifunctional, UV-curable perfluoropolyether-based elastomers for the fabrication of solvent-compatible microfluidic devices. We have pioneered very “user-friendly” materials and are collaborating with researchers in Applied Physics at Caltech and elsewhere for the fabrication of new lab-on-a-chip devices.

Gene Therapy and Drug Delivery: Another project involves the design, synthesis and detailed characterization of colloidal, non-viral vectors for gene and anti-sense therapies. We do this by using inverse microemulsion techniques as a template to design tailored nanohydrogel colloidal particles that have the requisite characteristics to shuttle, target, and release DNA/RNA into cells. These non-viral vectors can be designed with high specificity to target specific cell types through targeting ligands on their periphery and can also be designed to specifically release their payload to enhance cell infection. This project involves collaborations with researchers in the UNC School of Medicine, Gene Therapy and Pharmacy Departments.

Materials for Fuel Cells: Through our close working relationship with DuPont, we are designing new proton exchange membranes (PEM) for fuel cells. There is a strong need to improve the properties of NafionTM, which is the leading benchmark PEM. We are designing new materials based on tetrafluoroethylene and perfluorinated sulfonated vinyl ethers to make materials with higher glass transition temperatures and lower methanol permeability. Success in this project would allow the use of fuel cells at higher temperatures than is possible today, which would improve the efficiencies of the precious metal catalysts, and would also enable the use of methanol directly as the fuel source instead of hydrogen which has shipping and other logistical challenges. Much of our work is focused on the use of fuel cells for portable power applications such as laptops, cell phones, embedded sensors and applications in Homeland Security and the Department of Defense.

Microlithography: One of the key unit operations in the manufacture of integrated circuits and other microelectronic devices is lithography. Recently the University of North Carolina at Chapel Hill and North Carolina State University established the Triangle National Lithography Center (TNLC) with the purchase of a $10 million ASML 5500/950B 193 nm scanner. This stepper is capable of making sub-100 nm features on 200 mm wafers using optical lithography. We are pioneering the design of photoresists for use in next generation 157 nm and 193 nm lithography. Research is focused on materials that have low optical densities at these wavelengths, high etch resistance and the requisite dissolution characteristics for the fabrication of high resolution features.

Low-Surface-Energy Coatings for the U.S. Navy: One of the key research programs for the United States Navy is the design of coatings for ship hulls that can prevent biofouling—the accumulation of barnacles, algae and other living organisms. Biofouling of our ships dramatically increases the drag on the ships which slows them down, increases their acoustic signature and increases their consumption of fuel. We are designing non-toxic, minimally adhesive coatings that prevent the tenacious adhesion of living organism on the hull of ships allowing it to be “self-cleaning” when at elevated speeds due to simple shear forces.

All of the projects above exploit the synthetic capabilities of our group which often involves the design of new monomers and polymers, new curing chemistries and state-of-the-art polymerization methods including controlled radical, living anionic, and transition metal-catalyzed processes.

Chemistry in Liquid and Supercritical Carbon Dioxide:
Water and solvent usage is intrinsic to manufacturing in many different industries including chemical, microelectronic, biotech, textile, mining, automotive and aerospace just to mention a few. Our research group is focused on designing new methods that will replace “wet” processes based on water and organic solvents with “dry” processes based on the use of liquid and supercritical carbon dioxide (CO₂). Carbon dioxide is a promising alternative solvent for such manufacturing methods since it is environmentally benign, inexpensive, and easily recyclable. But most importantly for many of these processes, because CO₂ has an exceedingly low viscosity and surface tension, it is a superior solvent choice that enables better processes and the generation of better products at lower costs and faster production rates.

Microelectronics: The production of multi-layer integrated circuits is a complex, resource intensive process. In addition to chemical consumption and the resultant emissions, issues involving image collapse and low k dielectric materials are becoming increasingly important as the microelectronics industry looks towards the implementation of high aspect ratio single layer 193 nm resists and next generation 157 nm resists. There are several key unit operations that are responsible for a large fraction of the water, solvent, and chemical generation associated with integrated circuit manufacturing: a) cleaning and etching; b) lithography; c) dry organic and metal film deposition; and d) chemical mechanical planarization (CMP). My group is designing the chemical and mechanical methods necessary to replace the water and organic solvents in these unit operations with “dry” CO₂-based chemistries and processes. This project involves collaborations between chemists of all different types (inorganic, Organometallic, organic, colloid), along with chemical engineers and mechanical engineers.

Fluoroolefin Polymerizations: A cornerstone of our efforts has been to synthesize and process highly desirable polymeric products in an environmentally responsible way using liquid and supercritical CO₂ technologies. For the past several years, our goal has been to utilize the unique properties of supercritical fluids to improve the production of important specialty polymers based on tetrafluoroethylene such as TeflonTM, Teflon-AFTM, KalrezTM fluoroelastomers, NafionTM and other fluorinated high performance materials. We seek to increase the fundamental understanding of polymerization reactions through comparison of synthesis in traditional solvents and in CO₂ . For example, since supercritical fluids have the density and solvating power of liquids yet retain the diffusivity characteristics of a gas, they provide a unique opportunity to examine how solvent cage effects and viscosity properties affect basic reaction kinetics. Polymerization methods examined in our laboratory include homogeneous, precipitation, dispersion polymerizations, as well as continuous polymerization methods. We are also interested in the benefits imparted by CO₂ plasticization of polymers in melt phase and solid state polymerizations.

Surfactants for Liquid and Supercritical Carbon Dioxide: An exciting area in our group involves the design and study of surfactants for CO₂. This focus area finds application in areas such as biotechnology, extractions, precision cleaning, and catalysis. The development of novel surfactants tailored for use in CO₂ opens up possibilities for the highly specific recovery of substrates from mixed streams, including the selective removal of pharmaceuticals from fermentation broths and remediation of contaminated ground water. We are interested in the large effects that subtle changes in the density of CO₂ can have on the degree and nature of self assembly in CO₂ because of its high compressibility, in particular the dynamics of exchange and the reversible self assembly of block copolymer surfactants. We design new materials and collaborate with theorists and physical chemists to explore these details.