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Dharmaraj Raghavan

Professor of Chemistry

Polymer Chemistry

draghavan@howard.edu

202-806-4427(Voice)

202-806-5442 (FAX)

B.S. Chemistry, Bombay University, 1985,

M.S. Chemistry (Polymer), Indian Institute of Technology, 1987,

Ph. D. Material Science and Engineering, New Mexico Tech, 1990

Post-Doctoral Fellow, Material Science and Engineering, University of Illinois, 1993

Guest Scientist, Polymer Division and Building Material Division National Institute of Standards and Technology, Gaithersburg, 1993-present

Research Interests

Surface Modification, Thin Film and Coating Stability, Biomaterials

Research Summary

The highlight of our research has focused on the grand challenge the Design of Materials through Nanotechnology.  Our design protocol for material formulation has heavily relied on establishing fundamental structure-property relationship of nanomaterials.   Our work in the field of nanocomposites builds the connection between surface chemistry of high aspect ratio nanoclay platelets and bulk properties such as mechanical strength, adhesion, and morphology of nanoparticulate dispersed polymer.  One of the exciting possibilities of nanotechnology lies in the ability of nanoparticles under specific conditions to organize around the dispersed phase to form materials with highly desirable properties.  The extent of interaction at the interface and the arrangement of platelets in polymer matrix can impact the performance of nanocomposite.  Using the self assembled monolayer approach, we were able to probe the effect of covalent bonding, mechanical interlocking, and physicochemical interactions on the behavior of inorganic/organic polymeric system.  The performance of advanced composites, coatings, and biomaterial depend strongly on chemical (surface energy, chemical functionality, patterning of inorganic and organic materials) and physical (film thickness, processing temperature) variables. Combinatorial library preparation allows to rapidly screen the impact of diverse physical and chemical variables on the nanostructure of ultrathin coatings.  We were able to obtain a near universal scaling curve describing film stability for different molecular weights in the surface energy of the substrate and temperature variables, by introducing reduced variables.  The combinatorial approach has been extended to design biomaterial surfaces.  Our initial results show that interfaces of cell/biomaterial play a critical role in the cell behavior and in particular the interaction of synthetically designed materials with biological system.  Our efforts have demonstrated that high throughput approach that encompasses diverse surface and interface properties can be highly valuable in the design of biomaterials through nanotechnology.

PUBLICATIONS

  1. D. Raghavan, S. Goheen and R. P. Wool, Statics and Dynamics of Biodegradation of Polyethylene-Starch Composites, Bulletin of American Physical Society, 36(3), 631(1990).
  2. D. Raghavan, R. Guay and A. E. Torma, A Study of Biodegradation of Polyethylene and Biodesulfurization of Rubber, Applied Biochemistry and Biotechnology, 24, 387(1990).
  3. A. E. Torma and D. Raghavan, Biodesulfurization of Rubber, Bioprocess Engineering Symposium, R. M. Hochmuth, American Society of Materials Engineering NY, 1990, 81.
  4. D. Raghavan, A. Shaligram and D. D. Deshpande, The Influence of Charge Density and Steric Factors of Aminated Chloromethyl Polystyrene Homologs in Bilirubin Adsorption, Journal of Applied Polymer Science, 42, 2483(1991).
  5. R. P. Wool, D. Raghavan, S. Billieux and G. C. Wagner, Statics and Dynamics of Biodegradation in Polymer-Starch Blends, In : Biodegradable Polymers and Plastics, M. Vert, J. Feijen, A. C. Albertsson, G. Scott, and E. Chiellini, eds., Second International Scientific Workshop on Degradable Polymers and Plastics, Montpellier, France, 1991, 112-120.
  6. D. Raghavan and A. E. Torma, DSC and FTIR Characterization of Biodegradation of Polyethylene, Polymer Engineering and Science, 32(6), 438(1992).
  7. D. Raghavan, R. P. Wool and G. C. Wagner, Carbon Balance During Biodegradation of Polymer, Polymer Materials Science and Engineering, 67, 357(1992).
  8. D. Raghavan, G. C. Wagner and R. P. Wool, Aerobic Biometer Analysis of Glucose and Starch Biodegradation, Journal of Environmentally Degradable Plastics, 1(3), 203(1993).
  9. R. P. Wool and D. Raghavan, Biodegradation Rates of Polymer-Starch Blends in Aquatic Environments : Effects of Fractal Structure, ACS Polymer Preprints, 58, 206(1993).
  10. D. Raghavan, K. Tratt, and R. P. Wool, Recycled Rubber in Cement Composites, Materials Research Society Symposium Proceedings, 344, 177(1994).
  11. D. Raghavan, K. Tratt and R. P. Wool, Interfacial Bonding of Recycled Rubber Cement Composites, Processing of Advanced Materials, 5, 21(1994).
  12. D. Raghavan, Characterization of Degradable Plastics, Polymer Plastics Technology and Engineering, 34(1), 41(1995).
  13. D. Raghavan and James H. Johnson Jr., Comparison of Extraction Methodologies for Desorption of Pyrene from Contaminated Soil, Proceedings of 27th Mid-Atlantic Industrial Waste Conference, Technomic Publications, Lancaster, PA, 1995, 754.
  14. H. Huynh, D. Raghavan, C. Ferraris, Rubber Particles From Recycled Tires in Cementitious Composite Materials, National Institute of Standards and Technology Publication, IR5850, 1-19(1996).
  15. H. Huynh and D. Raghavan, Durability of Shredded Rubber Tires in Highly Alkaline Environments, Journal of Advanced Cement Based Materials, 6, 132(1997)
  16. K. Egwim, R. Ellis, D. Raghavan, W. R. Jones, and S. E. Broedel Jr., A Novel Approach  to Polymer Coating and Waste Disposal System, 1997 DoD/Aerospace Coating Conference, Las Vegas, NV, 1997, 19.
  17. D. Raghavan, H. Huynh and C. F. Ferraris,  Workability, Mechanical Properties and Chemical Stability of a Recycled Tire Rubber-Filled Cementitious Composites, Journal of Material Science, 33, 1745(1998).
  18. E. Feresenbet, Y. Abrha, D. Raghavan and James H. Johnson, Thermal Extraction of 2,3 dichlorobiphenyl From Coal Matrix, ACS Environmental Chemistry Preprints, 38, 152(1998).
  19. D. Raghavan, D. Hunston, J. He and D. Hoffman, The Influence of Morphology and  Concentration on Toughness in Dispersions Containing Preformed Acrylic Elastomer Particles in an Epoxy Matrix.  Polymer Material Science and Engineering, 79,194(1998).
  20. D. Raghavan, K. Egwim, R. Ellis, W. R. Jones and S. E. Broedel, Biodegradable Polymers for Stripping Polymer Coating Films, ACS Polymer Preprints, 39, 146(1998).
  21. J. He, D. Raghavan, D. Hunston, and D. Hoffman, The Influence of  Elastomer Concentration on                                     Toughness in Dispersions Containing Preformed Acrylic Elastomer Particles in an Epoxy Matrix, Polymer, 40, 1923(1999).
  22. M. VanLandingham, X. Gu, D. Raghavan, and T. Nguyen, Characterization of Multi-phase and Multi-component Polymer Systems Using the Atomic Force Microscope, Proceedings of Microscopy and Microanalysis, Portland, OR, Springer-Verlag, New York,  1999, 962.
  23. D. Raghavan, Study of Rubber-Filled Cementitious Composites, Journal of Applied Polymer Science, 77(4), 934(2000).
  24. D. Raghavan, X. Gu, T. Nguyen, M. VanLandingham, A. Karim, Mapping Polymer Heterogeneity By Phase Imaging And Nanoindentation AFM,  Macromolecules,  33(7), 2573(2000).
  25. R. P. Wool, D. Raghavan, G. C. Wagner, and S. Billieux, Biodegradation Dynamics of Polymer-Starch Composites, Journal of Applied Polymer Science, 77(8), 1643(2000).
  26. D. Raghavan and K. Egwim, Degradation of Polyester Film in Alkali Solution, Journal of Applied Polymer Science, 78(14), 2454(2000).
  27. D. Raghavan, M. VanLandingham, X. Gu, and T. Nguyen, Characterization of Heterogeneous Regions in Polymer Systems Using Tapping Mode and Force Mode Atomic Force Microscopy, Langmuir, 16(24), 2454(2000).
  28. Y. Abrha and D. Raghavan, PCB Recovery From Spiked Organic Matrix Using Accelerated Solvent Extraction (ASE) and Solvent Extraction, Journal of Hazardous Materials, B80,147 (2000).
  29. D. Hunston, J. He, D. Raghavan, and D. K. Hoffman, Limits on Toughening of Epoxies,  20th Proceedings of Adhesion Society Meeting,  Myrtle Beach, SC, 2000, 200.
  30. X. Gu, M. VanLandingham, D. Raghavan, and T. Nguyen,  Mapping Heterogeneity in Polymeric Materials Using  Atomic Force Microscopy Phase Imaging and Nanoindentation, Polymer Materials Science and Engineering, 82, 50(2000).
  31. G. A. Holmes, E. Feresenbet, E. Pohl, W. G. McDonough, D. Raghavan and D. Thompson, Factors That Affect Adhesion at the Fiber-Matrix Interface In Composites, 21st Adhesion Society Meeting, Savanah, GA, 2000, 382.
  32. D. Hunston, J. He, D. Raghavan, and D. Hoffman, Load History Dependence of Fracture  in Rubber-Toughened Epoxies, 21st Adhesion Society Meeting, GA, 2000, 10.
  33. X. Gu, D. Raghavan, T. Nguyen and M. VanLandingham, Characterization of Polyester   Degradation Using Tapping Mode Atomic Force Microscopy, Polymer Materials Science and Engineering, 83, 336(2000).
  34. D. Raghavan, X. Gu, M. VanLandingham and T. Nguyen, Mapping Chemical        Heterogeneous Polymer System Using Chemical Modification and Atomic Force Microscopy, ACS Polymer Preprints, 41(2), 1423(2000).
  35. T. Nguyen, J. Chin, D. Raghavan and A. Khaled, Sorption and Diffusion of Alkaline Solution in Organic Coatings at Ambient and Elevated Temperatures, Polymer Materials Science and Engineering, 83, 319(2000).
  36. D. Raghavan and A. Emekalam, Characterization of Starch/Polyethylene and Starch/Polyethylene/Poly(lactic acid) Composites, Polymer Degradation and Stabilization, 72,509(2001).
  37. D. Raghavan, X. Gu, M. VanLandingham, and T. Nguyen, Characterization of Chemical  Heterogeneity in Polymer Systems Using Hydrolysis and Tapping Mode Atomic Force    Microscopy, Journal of Polymer Science : Polymer Physics Edition, 39, 1460(2001).
  38. X. Gu, D. Raghavan, M. VanLandingham, T. Nguyen and D. Yebassa, Characterization of Degradation of Polyester Film Using Tapping Mode Atomic Force Microscopy : 1. Alkali Exposure, Polymer Degradation and Stabilization, 74,139(2001).
  39. D. Raghavan, US/Africa Workshop on Water and Environmental Quality, NSF/ACS Invitation, Dakar, Africa.
  40. D. Raghavan, X. Gu, M. VanLandingham, and T. Nguyen, Mapping Chemically Heterogeneous Polymer System Using Selective Chemical Reaction and Tapping Mode Atomic Force Microscopy, Macromolecular Symposia,  166, 297(2001).
  41. Karen  Ashley, J. Carson Meredith, D. Raghavan, E. Amis, and A. Karim Combinatorial Measurement of Dewetting of Polystyrene Thin Films, Polymer Communication, 44, 769(2003).
  42. G. A. Holmes, E. Fersenbet, and D. Raghavan, Using Self-Assembled Monolayer Technology To Probe The Fiber-Matrix Interface, 24th Adhesion Society Meeting, Richmond, VA, 2001, 62.
  43. E. Fersenbet, G. A. Holmes, and D. Raghavan, The Influence of Silane Coupling Agent on the Fiber Matrix Interfacial Shear Strength, 24th Adhesion Society Meeting, Richmond, VA, 2001, 502.
  44. G. A. Holmes, E. Fersenbet, and D. Raghavan, The Effect of Self-Assembled Monolayer Technology On Fiber-Matrix Adhesion, ACS Polymer Preprints, 42(1), 296(2001).
  45. X. Gu, T. Nguyen, M. R. VanLandingham and D. Raghavan, Effects of Crosslink Density on Surface and Interface Properties of Amine-Cured Epoxy, 25th Adhesion Society Meeting, Orlando, FL, 2002, 497.
  46. D. Raghavan, E. Feresenbet, D. Yebassa, A. Emekalam, and G. Holmes,  Dispersion of Functionalized Nanoclay Platelets in an Amine Cured Epoxy Resin System MRS Proceedings on Nanocomposite Materials, Boston, MA, 703, 2002, 399-406.
  47. X. Gu, D. Raghavan, D. L. Ho, M. VanLandingham, and T. Nguyen, Nanocharacterization of Surfaces and Interfaces of Different Epoxy Networks, MRS Proceedings on Surfaces and Interfaces, Boston, MA, 710, 2002, 153-158.
  48. D. Raghavan, E. Feresenbet, and G. Holmes, Application of Self Assembled Technology to Probe Fiber Adhesion, MRS Proceedings on Interfaces and Thin Films, Boston, MA, 710, 2002, 167-172.
  49. K. M. Ashley, A. Seghal, E. Amis, D. Raghavan, and A. Karim, Combinatorial Mapping of Polymer Film on Gradient Energy Surfaces, MRS Proceedings on Combinatorial and Artificial Intelligence Methods in Material Science, Boston, MA, 700, 2002, 151-156.
  50. A. Emekalam, X. Gu and D. Raghavan, Characterization of Renewable Composites, MRS Proceedings on Advanced Fibers, Plastics and Laminates, Boston, MA, 702, 252, 2002.
  51. D. Raghavan, J. He, D. Hunston, and D. Hoffmann, Strain Rate Dependence Of Fracture In a Rubber-Toughened Epoxy System, Journal of Adhesion, 78, 723 (2002).
  52. X. Gu, D. Raghavan, J. Douglass, and A. Karim, Dewetting of Unstable Bilayer Polymer Films, Journal of Polymer Science : Polymer Physics Edition, 40, 2825(2002)
  53. E. Fersenbet, G. A. Holmes, and D. Raghavan, The Influence of Silane Coupling Agent on the Fiber Matrix Interfacial Shear Strength, Journal of Adhesion, 79, 1(2002).
  54. S. Balakrishnan and D. Raghavan, Chemically Functionalized Clay Nanocomposite, NANOTECH 2003, 3, 247.
  55. G. Holmes, E. Fersenbet, and D. Raghavan, Using Self-Assembled Monolayer Technology to Probe the Mechanical Response of the Fiber Interphase-Matrix Interphase Interface, Composite Interfaces, 10, 510(2003).
  56. S. Balakrishnan and D. Raghavan, Synthesis of 13(14) Hydroxy-cis-10-Nonadecenyl amine hydrochloride, Journal of the American Oil Chemists Society, 80(5), 503(2003).
  57. D. Yebassa, S. Balakrishnan and D. Raghavan, Next Generation Nanocomposites Through Nanotechnology, NANOTECH 2003, 3, 251(2003).
  58. D. Yebassa, S. Balakrishnan, E. Feresenbet, D. Raghavan, P. R. Start, and S. D. Hudson, Chemically Functionalized Clay Vinyl Ester Nanocomposites : Effect of Processing Conditions,  J. Polym. Sci. Polym. Chem. Edn., 42, 1310 (2004).
  59. D. Raghavan, S. Balakrishnan and Y. Gebrekristios, Optimizing Processing Conditions to Influence the Morphology of Nanocomposites, NANOTECH 2003, 3, 243(2003).
  60. S. Balakrishnan and D. Raghavan, Acrylic Elastomeric Particle Dispersed Epoxy-Clay Hybrid Nanocomposite : Mechanical Properties, Macromolecular Rapid Communication, Macromolecular Rapid Communication, 25, 481(2004).
  61. N. Eidelman, D. Raghavan, A. M. Forster, E. J. Amis, and A. Karim, Combinatorial Approach to Characterizing Epoxy Curing, Macromolecular Rapid Communication, 25, 259(2004).
  62. S. Balakrishnan and D. Raghavan, Chemically Functionalized Clay Vinyl Ester Nanocomposite I. Vernonia Oil Based Surfactant, Journal of Reinforced Plastics and Composites, in print (2004).
  63. S. Balakrishnan and D. Raghavan, Mechanical Properties of Chemically Functionalized Clay Vinyl Ester Nanocomposites, MRS Proceedings on Mechanical Properties of Nanostructure Materials and Nanocomposites, Boston, MA, in print 2004.
  64. D. Raghavan, Chapter on Strategies for Reuse of Rubber Tires, Rubber Recycling, Edited by S. K. De and A. Isayev, CRC Publishers, 2004.
  65. R. Jones, L. Mulamula, S. Swaminathan, Y. Tesema, and D. Raghavan, Controlled release of β-estradiol from biodegradable polymeric microspheres, MRS Proceedings on Biomaterials for Drug Delivery, Boston, MA, in print 2004.
  66. X. Gu, D. Raghavan, and A. Emekalam, Combination of Atomic Force Microscopy and Chemical Hydrolysis to Characterize Degradable Regions in Polymer Blends, Polymer International, under review (2004).     
  67. A. M. Forster, D. Raghavan, N. Eidelman, and A. Karim, Combinatorial Technique to Measure Curing of Epoxy Film,  27th Adhesion Society Meeting, Wilmington, NC.
  68. Y. Tessema, D. Raghavan, and J. Stubbs, Osteoblast Activity on Biodegradable PHBV Membrane, Journal of Applied Polymer Science, in print (2004).
  69. S. Balakrishnan and D. Raghavan, Chemically Functionalized Clay Epoxy Nanocomposite II. Vernonia Oil Based Surfactant, Journal of Reinforced Plastics and Composites, submitted (2004).
  70. Y. Tessema, D. Raghavan, and J. Stubbs, Bone Cell Viability on Methacrylic acid Grafted and Collagen Immobilized Porous Poly(3-hydroxybutrate-co-3-hydroxyvalerate) Osteoblast Activity on Biodegradable PHBV Membrane, Journal of Applied Polymer Science, in preparation (2004).