Erdogan Kiran


Kiran\

Honors and Professional Recognition

  • Gottesman Research Professor of Chemical Engineering, University of Maine, 1986 -2000.
  • Member, AIChE High-Pressure Committee, 1986 - 1996.
  • Founding Editor, and Editor-in-Chief, Journal of Supercritical Fluids, 1987-present.
  • Editorial Board Member, Turkish Journal of Engineering and Environmental Sciences, 1989 - present.
  • Organizer and Chair, Symposium on Biopolymers in Supercritical Fluids, 199th ACS National Meeting, Boston, 1990.
  • Organizer and Co-chair, Symposium on Supercritical Fluids, AIChE Annual Meeting, Los Angeles, 1991.
  • Consulting Professor, Bilkent University, Turkey, 1991.
  • Who's Who in Science and Engineering, 1992.
  • Director and co-organizer, NATO Advanced Study Institute on Supercritical Fluids, Kemer, Turkey, 1993.
  • Organizer and chair, Symposium on Thermosetting Polymers, Princeton University, 1995.
  • University of Maine, Presidential Research and Creative Achievement Award, 1995.
  • Guest Lecturer, Department of Chemical Engineering and Food Science, University of Salerno, Italy, 1996.
  • Invited panelist, Chemical Engineering Science - Unilever Conference on Putting Structure into Chemical Engineering, Chester, UK, November 6 - 8, 1996.
  • Scientific Committee Member, 4th International Symposium on Supercritical Fluids, Sendai, Japan, 1997.
  • Director and co-organizer, 2nd NATO Advanced Study Institute on Supercritical Fluids, Kemer, Turkey, 1998.
  • International Monitor, The Journal of Chemical Engineering of Japan, 1999-2000.
  • Plenary Lecturer, 1st International Meeting on High Pressure Chemical Engineering, Karlsruhe, Germany, 1999.
  • Head, Department of Chemical Engineering, Virginia Tech, January 2000- September 2005.
  • Plenary Lecturer, 6th Conference on Supercritical Fluids and Their Applications, Maiori, Italy, 2001.
  • Organizing Committee Member, 4th International Symposium on High Pressure Process Technology and Chemical Engineering, Venice, Italy, 2002.
  • Organizer and Co-chair of sessions on Thermodynamics under High Pressure at the AIChE Annual Meeting, Indianapolis, 2002.
  • Plenary Lecturer, 5th Brazilian Meeting on Supercritical Fluids, Florianopolis, Brazil, 2004.
  • Scientific Committee Member, 3rd International Meeting on High Pressure Chemical Engineering, Erlangen, Germany, 2006.
  • Scientific Committee Member, 1st Iberoamerican Conference on Supercritical Fluids- PROSCIBA, Iguassu Falls, Brazil, 2007.
  • Plenary Lecturer, 5th International Symposium on High Pressure Processes Technology and Chemical Engineering, Segovia, Spain, 2007.
  • Plenary Lecturer, 1st International Symposium on Supercritical Fluid in Fiber /Textile Science and Technology, Tokyo, Japan, 2008.
  • Plenary Lecturer, Ruhr University-Bochum, Interdisciplinary Graduate Research School Symposium, Bochum, Germany, 2008.



Research Interests

  • Supercritical Fluids and High Pressure Techniques.
  • Microstructured and / or Functional Polymeric Materials.
  • Natural and Biodegradable Materials.



Supercritical Fluids and High Pressure Techniques

    Supercritical fluids are neither gas nor liquid but can be compressed gradually from low to high density. As a result a wide range of properties from gas-like to liquid-like become accessible by these fluids by simple manipulation of pressure and/or temperature. As such, these are tunable fluids that can be customized for a given application. They are ideal for selective and or sequential separations by pressure or density tuning. For example, depending upon the fluid density, the fluid may be tuned to behave as a specific solvent for a specific substance at one pressure, but as a non-solvent at another pressure.

    Historically, the pressure-tunable characteristics were first put to commercial practice in the selective extraction in the food industry as in decaffeination of coffee and tea. In the analytical field, these concepts were adopted in supercritical fluid chromatography that is also commercial. The applications have expanded dramatically in the past decade to include a wide range of operations that are encountered in various industries ranging from pharmaceuticals, to microelectronics.

P-T

The motivation in using supercritical fluids stem from the fact that:

  1. Their physicochemical properties can be conveniently changed by density or pressure-tuning, and can be further modified through compositional tuning when using binary fluid mixtures;
  2. They can be used not only as a solvent or diluents, but also as non- solvents;
  3. They can facilitate recycling of the solvent, removal of the solvent from the products, and the recovery of the products from the solvent, or facilitate the processing of traditional materials;
  4. They are easy to adopt for hybrid- or coupled-methodologies such as simultaneous reaction and separation, or modulated miscibility, phase separation and property modifications;
  5. They can be used as replacement of undesirable solvents, and be environmentally benign and / or less harmful compared to traditional organic solvents as is the case with carbon dioxide-based processes. Carbon dioxide is considered to be GRAS (generally regarded as safe) and is of special interest in processing of materials for pharmaceutical and medical applications.

Our research program is aimed at understanding both the equilibrium and time-dependent aspects of the physicochemical processes involving these fluids. In particular, the solubility, reactivity, and stability of various substances ranging from relatively simple molecules to complex synthetic or natural polymeric systems in single and multi-component fluids are being studied. Transport properties such as viscosity under supercritical or high pressure conditions are also being investigated. Specialized and often unique instrumentation are used for determination of miscibility and phase separation conditions; for determination of volumetric and flow properties; for assessment of the time scale and the mode of phase separation processes; and to carry out reactions, extractions, or targeted modifications.



Microstructured and/or Functional Polymeric Materials

The major focus in our research program is on polymer formation, modifications, and processing.

Polymerization in supercritical fluids is explored as a method to control polymer molecular weight, molecular weight distributions, and chain microstructure. Interactions of high pressure gases and fluids with polymers and polymer solutions in supercritical fluids are evaluated for various polymer processing operations. Equilibrium and dynamic aspects of polymer solutions are investigated with respect to dissolution and phase separation. Pressure-jump techniques are used to study the kinetics of phase separation and for identification of "nucleation and growth" and "spinodal decomposition" regimes. Pressure-induced phase separation is used to produce micro or nano-porous or micro-structured polymers and blends for applications related to foams, fibers, membranes, and scaffolds. Viscosity determinations are used to assess polymer chain mobility and chain dimensions in different solvents, under different temperature and pressure conditions. Crystallization and / or gelation from high-pressure conditions and the consequences of the phase separation paths on the final bulk or surface morphology are explored.

Practical application areas of interes are particle formation and encapsulation for controlled-release drugs; foaming and scaffolding for tissue engineering; crystal or morphological modifications for advanced applications involving fibers, membranes, or other microstructured- or functional - materials; and polymer synthesis with simultaneous morphology development.



Natural and Biodegradable Materials

Our interest in natural materials is focused on understanding the physico-chemical properties and processing of natural polymers such as lignocellulosic materials. Thermal, solvent, or chemical modification and separation procedures are being explored for novel processes such as supercritical delignification for sulfur and chlorine-free pulping and bleaching operations, environmentally acceptable solvents for processing of cellulose derivatives, supercritical impregnation processes for property modifications, and supercritical hydrolysis and depolymerization. We also have interest supercritical fluid-based modifications and cleaning of coal. Biodegradable polymers and materials are being explored for medical and pharmaceutical applications ranging from controlled release to tissue engineering.



Selected Examples from Recent Research

Our research activities are at the cross-sections of Polymers, Supercritical Fluids, and High Pressure Techniques.

Below are some examples of recent research from

    Polymer Crystallization or Gelation
    Polymer Foaming
    Polymerization
    Polymer Miscibility and Phase Separation
    Viscosity



Polymer Modification via Crystallization or Gelation, and Polymer Foaming

Crystallization or re-crystallization of polymers in dense fluids at high pressures is creating new opportunities for formation of particles or novel morphologies from semi-crystalline polymers. Crystallization can be carried out at constant pressure, temperature, or density with different levels of undercooling. The path that is followed greatly influences the crystal morphology (shape and the polymorphic state) that develops.

Polymer foaming in or with supercritical fluids also offers new opportunities in a wide range applications involving porous materials. Miscibility of the fluid with the polymer is achieved under pressure. When depressurized, the fluid-swollen polymer is transformed into a micro- or nano-porous material. The final morphology depends on the kinetics of phase separation, and the kinetics of the thermal transformation (crystallization and/or vitrification) of the polymer matrix, as well as the changing dynamics on viscosity and interfacial tension. Foams with a varying pore distribution or multimodal pores, nano-foams, closed- versus open-cell morphologies are of continuing interest.

  1. Polyethylene can be crystallized from solutions in n-pentane + carbon dioxide in highly uniform lamellar morphologies which can be controlled with pressure. [W. Zhang, E. Kiran, J. Supercritical Fluids, 38, 406, 2006].

    2.       

  2. Depending upon the pressure / temperature conditions, poly(e-caprolactone), a biodegradable polymer, can be recrystallized or foamed when exposed to supercritical carbon dioxide. [E. Kiran, K. Liu, K. Ramsdell, Polymer, 49, 1853, 2008].

    3.       

  3. Different polymorphic states with fibrillar–porous (delta polymorph) or lamellar (beta polymorph) morphology of syndiotactic polystyrene can be generated by crossing first the sol-gel boundary, or the liquid-liquid boundary, respectively, in toluene + carbon dioxide solutions. [J. Fang, E. Kiran, Macromolecules, 41, 7525, 2008].

    4.       

  4. Microporous polymers with a spacially-varying pore distribution or with bimodal porosity can be generated by sorption and depressurization of supercritical fluid mixtures within the polymer. [Z. Bayraktar, E. Kiran, J. Supercritical Fluids, 44, 48, 2008].

    5.       



Polymerization

Polymerizations and copolymerizations in supercritical fluids are of great interest. These processes are intriguing in that with the progress of polymerization the fluid compositions and the viscosity of the medium change. The change in the fluid composition along with the increase in the molecular weight of the polymer formed continually alters the phase boundaries. In copolymerizations, the initial monomer ratio employed and pressure and the temperature conditions determine the copolymer composition and the conditions of phase separation and the final morphologies. The end result ranges from fine particles if the copolymer is semicrystalline and undergoes solid-fluid phase separation, to porous matrices if copolymer formed is glassy and is swollen in the reaction mixture.


  1. The precipitation copolymerization of acrylonitrile with 2-chlorostyrene and methyl methacrylate lead to different particle morphologies at the same comonomer contents. [S. D. Yeo and E. Kiran, Macromolecules, 37, 8239, 2004].

    2.       

  2. Real-time simultaneous assessment of changes in density and viscosity with time provide new insights on polymerization processes such as polymerization of methyl metyhcarylate in acetone. [K. Liu, E. Kiran, Ind. & Eng. Chem.- Research, 47, 5039, 2008].

    3.     



    Polymer Miscibility and Phase Separation

    Polymer miscibility and phase separation of polymers at high pressures in supercritical fluids are key steps involved in essentially all applications related to polymer modification and processing. We are especially interested in phase behavior and the miscibility of polymers in binary fluid mixtures. The fluid mixtures that we are of primary interest are those containing carbon dioxide as a component. Binary fluid mixtures introduce fluid composition as an additional tuning parameter to pressure or density in adjusting the miscibility and phase separation conditions for a given polymer. Such binary mixtures naturally arise for example in polymerization reactions in carbon dioxide, which are basically reactions that proceed in mixture of carbon dioxide and the monomer itself.

    The figure below shows the miscibility conditions for polysulfone in binary mixtures of carbon dioxide and tetrahydrofuran. [W. Zhang and E. Kiran, J. Appl. Poly. Sci., 86, 2357, 2002]. The region above each curve represents the miscible region. As the solvent power is reduced with increasing the carbon dioxide content in the fluid mixture, pressures required to achieve miscibility increase, and the temperature sensitivity change sign.





    High Pressure Viscosity of Polymer Solutions

    Viscosity of polymer solutions is an extremely important transport property that plays a critical role in polymer formation, or in polymer processing ranging from formation of particles to fibers. A topic of particular interest is the reduction of viscosity in the presence of carbon dioxide as a diluent. Our group has been systematically investigating the viscosity of polymer solutions and their dependence on pressure, temperature, fluid composition, polymer type, concentration and molecular weight using a falling-cylinder type viscometer which also provides densities. These data are correlated with solution density, ρ, and close-packed volume, Vo, using Doolittle type equations, i.e., η = C exp [D/ (1-ρV0)] .

    The figure below is such a plot for a solution of ploy (methyl methacrylate) in acetone + carbon dioxide mixtures. [[K. Liu, F. Schuch, E. Kiran, J. Supercritical Fluids, 39, 89, 2006]. In the presence of carbon dioxide, at a given density, viscosity is lower in systems that contain more carbon dioxide. If same viscosity level is to be reached, the solutions containing more carbon dioxide must be compressed to higher densities.



    Members of the Research Team and Collaborators

    (2000 - Present)

      Zeynep Bayraktar (Visiting researcher, 2000)
      Ke Liu (Visiting researcher, 2000)
      Prof. Sang-Do Yeo (Visiting scholar 2004)
      Cigdem Dindar (MS, 2001)
      Gerd Upper (Diploma Thesis, 2002)
      Daniel Beckel (Diploma Thesis, 2002)
      Frank Schuch (Diploma Thesis, 2003)
      Christopher Kornmeyer (Diploma Thesis, 2004)
      Jan Koop (Diploma Thesis, 2004)
      Elizabeth Joyce (Undergraduate Independent Research, 2004)
      Katrina Ramsdell (Undergraduate Independent Research, 2005)
      Wei Zhang (Ph. D., 2005)
      Kun Liu (Ph.D., 2007)
      Jian Fang (Ph.D., 2008)
      Prof. John Hassler


        


        



    Facilities

    Laboratory is equipped with high-pressure instrumentation for investigations of thermo-physical properties of fluids and polymer solutions.

    Facilities include unique variable-volume view cells, and laser light scattering systems, and a viscometer for investigation of miscibility and phase separation in polymer solutions at pressures up to 1000 bar.


    Selected Publications

    The Journal of Supercritical Fluids

    This journal is currently a top-10 Chemical Engineering Journal with respect to its impact factor. It was founded by Professor Kiran in 1987. The first issue appeared in December 1988. Professor Kiran has been the Editor-in-Chief since then.

    January 2009 issue is a commemorative 20th year anniversary issue in which editorial board members review the past two decades of research and developments and provide perspectives and insights on the future directions in various application areas of the supercritical fluid science and technology.



    Journal homepage - www.elsevier.com/locate/supflu



    Books

    1. E. Kiran and J. F. Brennecke (Editors), Supercritical Fluid Engineering Science, ACS Symposium Series, No. 514, American Chemical Society: Washington, D.C., 1993. [410 pages].
    2. E. Kiran and J. M. H. Levelt Sengers (Editors), Supercritical Fluids-Fundamentals for Application, NATO ASI Series E: Applied Sciences- Vol. 273, Kluwer Academic Publishers: Dordrecht, Netherlands, 1994. [796 pages].
    3. E. Kiran, P. G. Debenedetti and C. J. Peters, Supercritical Fluids: Fundamentals and Applications, NATO ASI Series E: Applied Sciences- Vol. 366, Kluwer Academic Publishers: Dordrecht, Netherlands, 2000. [596 pages].

      



    Selected Journal Articles

    (2000 - present)

    1. Y. Xiong and E. Kiran, Kinetics of pressure-induced phase separation (PIPS) in polystyrene + methylcyclohexane solutions at high pressures, Polymer, 41, 3759-3777 (2000).
    2. Z. Bayraktar and E. Kiran, Miscibility, phase separation, and volumetric properties of solutions in poly (dimethylsiloxane) in supercritical carbon dioxide, Journal of Applied Polymer Science, 75, 1379 -1403 (2000).
    3. Y. B. Melnichenko, E. Kiran , K. D. Heath, S. Salaniwal, H. D. Cochran, M. Stamm, W. A. van Hook, and G. D. Wignall, Comparison of the behavior of polymers in supercritical fluids and organic solvents via small angle neutron scattering, Journal of Applied Crystallography, 33, 682 - 685 (2000).
    4. S. D. Yeo and E. Kiran, High-pressure viscosity of polystyrene solutions in toluene + carbon dioxide binary mixtures, Journal of Applied Polymer Science, 75, 306 - 315 (2000).
    5. K. Liu and E. Kiran, Pressure-induced phase separation in polymer solutions. Kinetics of phase separation and crossover from nucleation and growth to spinodal decomposition in solutions of polyethylene in n-pentane, Macromolecules, 34, 3060 - 3068 (2001).
    6. E. Kiran and K. Liu, The miscibility and phase separation of polyethylene with poly(dimethylsiloxane) in near-critical pentane, Korean Journal of Chemical Engineering, 19, 153 - 159 (2002).
    7. C. Dindar and E. Kiran, High-pressure viscosity and density of polymer solutions at the critical polymer concentration in near-critical and supercritical fluids, Industrial & Engineering Chemistry- Research, 41, 6354 - 6362 (2002).
    8. C. Dindar and E. Kiran, Reliable method for determination of the velocity of a sinker in a high-pressure falling body type viscometer, Review of Scientific Instruments, 73, 3664 - 3670 (2002).
    9. W. Zhang and E. Kiran, Phase behavior and density of polysulfone in binary fluid mixtures of tetrahydrofuran and carbon dioxide under high pressure: Miscibility windows, Journal of Applied Polymer Science, 86, 2357- 2362 (2002).
    10. S. D. Yeo, I. Kang and E. Kiran, Critical polymer concentrations of polyethylene solutions in pentane, Journal of Chemical & Engineering Data, 47, 571 - 574 (2002).
    11. W. Zhang and E. Kiran, PVT behavior and miscibility of ternary system polysulfone +THF + CO2 at high pressures, Journal of Chemical Thermodynamics, 35, 597- 615 (2003).
    12. W. Zhang, C. Dindar, Z. Bayraktar, and E. Kiran, The phase behavior, density and crystallization of polyethylene in n-pentane and in n-pentane + CO2 at high pressures, Journal of Applied Polymer Science, 89, 2201 - 2209 (2003).
    13. S. D. Yeo and E. Kiran, Copolymerization of acrylonitrile with methyl methacrylate and 2-chlorostyrene in supercritical CO2, Macromolecules, 37(22), 8239 - 8248 (2004).
    14. S. D. Yeo and E. Kiran, Formation of polymer particles with supercritical fluids, Journal of Supercritical Fluids, 34(3), 287- 308 (2005). [This manuscript is listed among the all-time top-10 cited papers published in this journal].
    15. G. Upper, W. Zhang, D. Beckel, S. Shon, K. Liu and E. Kiran, Phase boundaries and crystallization in polyethylene in-n-pentane and n-pentane + carbon dioxide fluid mixtures, Industrial & Engineering Chemistry-Research, 45, 1478 - 1492 (2005).
    16. J. Fang and E. Kiran, Crystallization and gelation of isotactic poly (4-methyl-1-pentene) in n-pentane and n-pentane + CO2 at high pressures, Journal of Supercritical Fluids, 38, 132 - 145 (2006).
    17. W. Zhang and E. Kiran, High pressure crystallization and melting of polyethylene in n-pentane, Journal of Supercritical Fluids, 38, 406 - 419 (2006).
    18. K. Liu, F. Schuch, E. Kiran, High pressure viscosity and density of poly(methyl methacrylate) + acetone and poly(methyl methacrylate) + acetone + CO2 systems, Journal of Supercritical Fluids, 39, 89 - 101 (2006).
    19. K. Liu and E. Kiran, Miscibility, viscosity and density of poly(e-caprolactone) in acetone + carbon dioxide binary fluid mixtures, Journal of Supercritical Fluids, 39, 192 - 200 (2006).
    20. J. Fang and E. Kiran, Kinetics of pressure-induced phase separation in polystyrene + acetone solutions at high pressures, Polymer, 47, 7943- 7952 (2006).
    21. K. Liu and E. Kiran, Viscosity, density and excess volume of acetone + carbon dioxide mixtures at high pressures, Industrial & Engineering Chemistry- Research, 46, 5453 - 5462, (2007).
    22. K. Liu and E. Kiran, A tunable mixture solvent for poly(ε-caprolactone): Acetone + carbon dioxide, Polymer, 48, 5612 - 5625 (2007).
    23. Z. Bayraktar and E. Kiran, Gradient blending of poly(dimethylsiloxane) with polystyrene and polyethylene in supercritical carbon dioxide, Journal of Supercritical Fluids, 44, 48 - 61 (2008).
    24. E. Kiran, K. Liu, K. Ramsdell, Morphological changes in poly (ε-caprolactone) in dense carbon dioxide, Polymer, 49, 1853 - 1859 (2008).
    25. K. Liu and E. Kiran, High pressure solution blending of poly(ε-caprolactone) with poly(methyl methacrylate) in acetone + carbon dioxide, Polymer, 49, 1555-1563 (2008).
    26. K. Liu and E. Kiran, Density and viscosity as real time probes for progress of high-pressure polymerizations: Polymerization of methyl methacrylate in acetone, Industrial & Engineering Chemistry- Research, 47, 5039 - 5047 (2008).
    27. J. Fang and E. Kiran, Thermoreversible gelation and polymorphic transformations of syndiotactic polystyrene in toluene and toluene + carbon dioxide fluid mixtures at high pressures, Macromolecules, 41, 7525 - 7535 (2008).
    28. E. Kiran, Polymer miscibility, phase separation, morphological modifications and polymorphic transformations in dense fluids, Journal of Supercritical Fluids, 47, 446-483 (2009).
    29. E. Kiran, G. Brunner, R. L. Smith, The 20th anniversary of the Journal of Supercritical Fluids- A special issue on future directions in supercritical fluid science and technology , Journal of Supercritical Fluids, 47, 333-335 (2009).
    30. J. Fang and E. Kiran, Gelation, crystallization and morphological transformations of syndiotactic polystyrene in acetophenone and acetophenone + carbon dioxide mixtures at high pressures, Journal of Supercritical Fluids, in press.



    Invited Seminars at Academic Institutions

    (2000 - present)

    1. "Polymer solutions at high pressures. Miscibility, phase separation and blending in supercritical fluids", Department of Chemical Engineering, University of Virginia, October 5, 2000.
    2. "Polymer modification in dense and supercritical fluids- A pathway to microstructured materials, School of Pharmacy, University of London, United Kingdom, December 2, 2002.
    3. "High pressure miscibility and phase separation in polymer solutions" Institute for Physical Chemistry, University of Bochum, Germany, December 5, 2002,
    4. "High pressure miscibility and phase separation in polymer solutions", Institute for Physical Chemistry, University of Dortmund, Germany, December 6, 2002.
    5. "Miscibility and phase separation in polymer solutions in dense fluids - High pressure pathways for formation of microstructured materials", Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina, April 7, 2003.
    6. "Miscibility and phase separation in polymer solutions in dense fluids. Challenges and opportunities", Department of Chemical Engineering, West Virginia University, Morgantown, West Virginia, March 5, 2004.
    7. "High-pressure miscibility and phase separation in polymer solutions", Chemical Engineering Department, University of California at Los Angeles, May 7, 2004.
    8. "Morphological modifications of polymers in dense fluids", Chemical and Biological Engineering Department, Virginia Commonwealth University, Richmond, Virginia, October 4, 2006.
    9. "Polymer solutions in dense fluids: Crystallization, gelation and morphological modifications", Department of Chemical and Biological Engineering, Koc University, Istanbul, Turkey, June 3, 2008.
    10. "Polymers, Dense Fluids, Functional Materials", Interdisciplinary Research School, Ruhr University-Bochum, Bochum Germany, November 6, 2008.






Department of Chemical Engineering
Virginia Polytechnic Institute and State University
133 Randolph Hall
Blacksburg, Virginia 24061
540 231 6631
540 231 5022 (fax)