Walter P. Murphy Professor of Chemical Engineering and of Materials Science and Engineering

Director, The Materials Research Center

BS, chemical engineering, 1978 University of Wisconsin

PhD, chemical engineering, 1983 University of Minnesota

Contact Info

 

Polymers: dynamics, films, polymerization, phase behavior

     We are using an environmentally benign pulverization process to achieve compatibilization of immiscible polymer blends and are investigating the molecular scale mechanisms of compatibilization. We have also shown that pulverization is useful in producing well-exfoliated polymer-clay nanocomposites.
     We have developed optical sensors to characterize the glass transition temperature, gelation, and physical aging in polymers and have found great differences in behavior of nanoconfined, ultrathin films relative to bulk. We have also used single-molecule spectroscopy and simulation to follow probe diffusion in polymers, providing an explanation of how diffusion of small molecules whose motion is coupled to cooperative segmental mobility is affected by nanoscale dynamic heterogeneity. We are also developing optical sensors as pressure-sensitive paints and systems for cure monitoring.
     We are achieving understanding of the role that oligomer and polymer radical diffusion plays in autoacceleration of free radical polymerization. This work, combining experiment with simulation, has also revealed the role of chain transfer reactions in mitigating reaction runaway. Controlled radical polymerization methods are also used to prepare and study a new class of polymers called gradient copolymers.

Prof. Torkelson's Research Group

 

Associations and Awards

Executive Committee of the Division of Polymer Physics of the American Physical Society, 2005-2008

Polymer Physics Prize (awarded by the Journal of Polymer Science Part B: Polymer Physics), 2004

Best Paper Award, Polymer Analysis Division, Society of Plastics Engineers, 2004

Charles M.A. Stine Award from the Materials Engineering and Science Division of the American Institute of Chemical Engineering, 2004

Director, Materials Research Center, Northwestern University, 2003-2006

Caterpillar Distinguished Lecturer, Dept. of Chemical and Biochemical Engineering, University of Iowa, 2002

Chair, Materials Engineering and Science Division, American Institute of Chemical Engineers, 2001-02

Fellow, American Physical Society, 1999

Associate Dean for Graduate Studies and Research, · McCormick School of Engineering, Northwestern University, 1997-2002

Bette and Neison Harris Professor of Teaching Excellence, 1995-98

Associated Student Government Faculty Honor Roll, 1995-96

McCormick School Advisor of the Year, 1993-94

NSF Presidential Young Investigator Award, 1987-92

Ralph A. Teetor Award (Society of Automotive Engineers), 1986

Lilly Foundation Teaching Fellowship, 1985-86

Tau Beta Pi Outstanding Teaching Award, 1984

Technological Institute (now McCormick School) Teacher of the Year, 1984-85

 

Publications

Model polymer nanocomposites provide undertanding of confinement effects in real nanocomposites [with P. Rittigstein, R.D. Priestley, and L.J. Broadbelt] Nature Materials 6: 278-282 (2007).

Eliminating the Enhanced Mobility at the Free Surface of Polystyrene:  Fluorescence Studies of the Glass Transition Temperature in Thin Bilayer Films of Immiscible Polymers [with C.B. Roth, K.L McNerny, and W.F. Jager] Macromolecules 40: 2568-2574 (2007).

Effect of spatial confinement on the glass transition temperature of patterned polymer nanostructures [with M.K. Mundra, S.K. Donthu, and V.P. Dravid] Nano Letters 7: 713-718 (2007).

Achievement of Quasi-Nanostructured Polymer Blends by Solid-State Shear Pulverization and Compatibilization by Gradient Copolymer Addition [with Y. Tao and J. Kim,] Polymer 47: 6773-6781 (2006).

Uniquely Broad Glass Transition Temperatures of Gradient Copolymers Relative to Random and Block Copolymers Containing Repulsive Comonomers [with J. Kim, M. Mok, R. Sandoval, D.J. Woo] Macromolecules 39: 6152-6160 (2006).

Structural Relaxation of Polymer Glasses at Surfaces, Interfaces and in between [with R.D. Priestley, C.J. Ellison,  and L.J. Broadbelt] Science 309: 456-459 (2005).