Supercritical Fluids Research Lab

Principal investigator:

Mark A. McHugh, Ph.D.
Phone: (804) 827-7031
Email: mmchugh@vcu.edu
Lab: Room 445

Supercritical fluid solvents are normally gases at room conditions, but, at high pressures, they become “tunable” solvents which exhibit advantages especially when applied as environmentally preferable solvents for a wide range of processes.[5] CO2 is an attractive SCF solvent since it is nontoxic, inexpensive, nonflammable and pharmacologically acceptable. The schematic diagram in Figure 1 shows a few of the ways CO2-based technology has been used to create novel materials, such as solid crystals used for pharmaceutical applications [6], conductive polymeric foams [7], scaffolds [8] and micro-to-nanocellular structures[1] used as fuel cell membranes and artificial tissues.

The other picture shows an example of the fundamental research we perform. The VCU undergraduate in this picture is performing high-pressure, small angle neutron scattering studies of polymer-SCF mixtures to obtain fundamental information on solvent quality. The challenge inherent in any new SCF-based technology is to develop an efficient design and process strategy to create hybrid materials with the desired product performance characteristics. This challenge can only be met through a deep understanding of the thermodynamics and transport properties of SCF-solute mixtures.  

Figure 1. Schematic of the types of SCF-based materials processing using CO2 to create foams [1], particles [2], fibers [3] and templated structures [4].

David Rock, a VCU undergraduate, performs SANS experiments with polymer-SCF mixtures at the National Institute of Standards and Technology, Gaithersburg, MD.

Our research group aims to exploit the underlying physics and chemistry of SCF-assisted technologies by merging it with materials science technologies to create materials with unique morphology and function not attainable by any other means. We utilize novel high pressure/temperature experimental techniques and an experimental design that reveals fundamental information at a molecular level. For example, we perform solution behavior and light scattering or SANS experiments over wide pressure and temperature ranges to modulate and identify molecular interactions between the components in solution. Our design protocol is to vary systematically both the molecular structure of the SCF solvent and the substance of interest. The information generated in our research provides a stringent test of solution theories and computer simulations being developed to predict phase behavior.

From our research we have identified new ways to use SCF solvents to create polymer-coated powders that are used in the pharmaceutical and polymers industries, to process polymeric-based, guest-host materials that offer enhanced product performance in the flavors and consumer products industries, and to process Teflon-type fluoropolymers that are the next-generation materials for the medical and electronics industries. Our research efforts are supported by corporate and government groups looking to capitalize on the unique characteristics of SCF solvents.

References

  1. H. Yokoyama, K. Sugiyama, Macromolecules 38 (2005) 10516-10522.
  2. M.Y. Kim, Y.W. Lee, H.-S. Byun, J.S. Lim, Ind. Eng. Chem. Res. 45 (2006) 3388-3392.
  3. Z. Shen, B.E. Thompson, M.A. McHugh, Macromolecules 39 (2006) 8553-8555.
  4. R. Butler, I. Hopkinson, A.I. Cooper, J. Am. Chem. Soc. (2003) 14473-14481.
  5. M.A. McHugh, V.J. Krukonis, Supercritical Fluid Extraction: Principles and Practice, 2nd ed., Butterworth-Heinemann, Boston, 1994.
  6. S.-J. Park, S.-Y. Jeon, S.-D. Yeo, Ind. Eng. Chem. Res. 45 (2006) 2287-2293.
  7. S.L. Shenoy, P. Kaya, C. Erkey, R.A. Weiss, Syn. Metals 123 (2001) 509-514.
  8. J.J.A. Barry, S.N. Nazhat, F.R.A.J. Rose, A.H. Hainsworth, C.A. Scotchford, S.M. Howdle, J. Mater. Chem. 15 (2005) 4881-4888.