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Search Publications by: Jack F. Douglas (Fed)

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Displaying 176 - 200 of 355

Polymer-Surface Interactions in Nanfilled Polymers

October 16, 2008
Author(s)
Alamgir Karim, Jack F. Douglas, A Nakatani, Eric J. Amis, D B. Majumdar
We review recent investigations of conventional and nanoparticle filled polymers using atomic force and optical microscopy, scattering (x-ray, neutron and visible light) to characterize the influence of filler particles on the phase separation morphology

Spinodal Dewetting on Chemically Patterned Substrates

October 16, 2008
Author(s)
A Sehgal, V Ferreiro, Jack F. Douglas, Eric J. Amis, Alamgir Karim
We utilize chemically patterned substrates with arrays of progressively narrower stripes (1-15 mm) to investigate the influence of pattern size on the morphology of dewetting polystyrene films. The early-stage dewetting patterns align with the substrate

Swelling of Grafted Polymer Brushes

October 16, 2008
Author(s)
Jack Douglas, M S. Kent, Sushil K. Satija, Alamgir Karim
The end-grafting of polymer chains to surfaces provides a robust method for modifying surface properties. Such layers are increasingly being employed in applications-modifying the biocompatibility of implants, the wetting, adhesive and frictional

Wetting-Dewetting Transition Line in Thin Polystyrene Films

October 16, 2008
Author(s)
K M. Ashley, D T. Raghavan, Jack F. Douglas, Alamgir Karim
Thin polymeric films are increasingly being utilized in diverse technological applications and it is crucial to have a reliable method to characterize the stability of these films against dewetting. The parameter space that influences the dewetting of thin

Quantifying Changes in the Fast Dynamics of Mixtures by Dielectric Spectroscopy

September 26, 2008
Author(s)
Tatiana Psurek, Christopher L. Soles, Kirt A. Page, Marcus T. Cicerone, Jack F. Douglas
The addition of a solvent or nanoparticles to a polymeric material can lead toappreciable changes in the rates of relaxation and reaction that can profoundly alter material properties and function. We introduce a general theoretical strategy for

Nanoimprint Lithography and the Role of Viscoelasticity in the Generation of Residual Stress in Model Polystyrene Patterns

June 10, 2008
Author(s)
Yifu Ding, Hyun Wook Ro, Jing N. Zhou, Brian C. Okerberg, Jack F. Douglas, Alamgir Karim, Christopher L. Soles
Understanding polymer deformation during the nanoimprinting process is key to achieve robust polymer nanostructures. Information regarding the process can be extracted from monitoring the decay of the imprinted polymer patterns during thermal annealing. In

Model for Reversible Nanoparticle Assembly in a Polymer Matrix

January 8, 2008
Author(s)
Andrew Rahedi, Jack F. Douglas, Francis W. Starr
The clustering of nanoparticles (NP) within solutions and polymer melts depends sensitively on the strength and directionality of the NP interactions involved, as well as the molecular geometry and interactions of the dispersing fluids. Since clustering

Block Copolymer Ordering With a Spatiotemporally Inhomogeneous Mobility

November 20, 2007
Author(s)
August W. Bosse, Jack F. Douglas, Brian Berry, Ronald L. Jones, Alamgir Karim
Motivated by recent measurements of zone annealing in block copolymer films at low temperatures, we implement a spatiotemporal mobility gradient with intrinsic variations associated with dynamic heterogeneities in the saddle point relaxation of a diblock

Atomic Motion During the Migration of General [001] Tilt Grain Boundaries in Ni

August 24, 2007
Author(s)
Hao Zhang, David J. Srolovitz, Jack F. Douglas, James A. Warren
We generalize a previous study of the atomic motions governing grain boundary migration to consider arbitrary misorientations of [001] tilt boundaries. Our examination of the nature of atomic motions employed three statistical measures: the non-Gaussian

Relaxation Behavior of Polymer Structures Fabricated by Nanoimprint Lithography

August 14, 2007
Author(s)
Yifu Ding, Hyun Wook Ro, Thomas A. Germer, Jack F. Douglas, Brian C. Okerberg, Alamgir Karim, Christopher L. Soles
We study the decay of the imprinted polystyrene (PS) patterns under thermal annealing using light diffraction. The first order diffraction intensity from the imprinted gratings was measured as a function of annealing time. Local intensity maximum is

Characterization of the Potential Energy Landscape in an Antiplasticized Polymer

July 6, 2007
Author(s)
Robert A. Riggleman, Jack F. Douglas, J J. de Pablo
Transition state searches have been performed on model coarse-grained polymer systems, and the results compared to those of an antiplasticized polymer system, which have been previously shown to be fragile and strong glass-forming systems, respectively. It

Tuning Polymer Melt Fragility With Antiplasticizer Additives

June 19, 2007
Author(s)
Robert A. Riggleman, Jack F. Douglas, J J. de Pablo
A polymer-diluent model exhibiting antiplasticization has beendeveloped and characterized by molecular dynamics simulations. Antiplasticizer molecules are shown to decrease the glass transition temperature Tg, but to increase the elastic moduli of the

Relationship between dispersion metric and properties of PMMA/SWNT nanocomposites

June 13, 2007
Author(s)
Takashi Kashiwagi, Jeffrey Fagan, Jack F. Douglas, Kazuya Yamamoto, N. Alan Heckert, Stefan D. Leigh, Jan Obrzut, Fangming Du, Minfang Mu, Sheng Lin-Gibson, K Winey, R Haggenmueller
Particle spatial dispersion is a crucial characteristic of polymer composite materials and this property is recognized as especially important innanocomposite materials due to the general tendency of nanoparticles to aggregate under processing conditions

Polymer Viscoelasticity and Residual Stress Effects on Nanoimprint Lithography

May 24, 2007
Author(s)
Yifu Ding, Hyun Wook Ro, Jack F. Douglas, Ronald L. Jones, Daniel R. Hines, Alamgir Karim, Christopher L. Soles
We examine the influence of viscoelastic effects on the stability of nanoimprinted polymer films. The decay of features for polymers below the critical entanglement molecular mass at elevated temperatures is determined by simple surface tension and the