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Search Publications by: Jack F. Douglas (Assoc)

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Displaying 201 - 225 of 361

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

Computer Simulations of Ionomer Self-Assembly and Dynamics

May 17, 2007
Author(s)
Moonjoy Goswami, S K. Kumar, Aniket Bhattacharya, Jack F. Douglas
Computer simulations of a model telechelic ionomer, i.e. a melt with a charge at each chain end along with neutralizing counterions, indicate a form of self-assembly that is hybrid between the packing driven interactions in block copolymers and the

Crystallization of Polyethylene Oxide Patterend by Nanoimprint Lithography

March 28, 2007
Author(s)
Brian C. Okerberg, Christopher L. Soles, Jack F. Douglas, Hyun Wook Ro, Alamgir Karim
The crystallization behavior of poly(ethylene oxide) (PEO) films patterned by nanoimprint lithography is studied. The imprinted PEO film consists of parallel lines, approximately 240 nm wide and 320 nm tall, on a 400 nm pitch with a residual layer of

Numerical Path-Integration Technique for the Calculation of Transport Properties

March 13, 2007
Author(s)
E Kang, M Mansfield, Jack F. Douglas
We present a new technique for the computation of both the translational diffusivity and the intrinsic viscosity of macromolecules, and apply it here to approximately 1000 different protein structures. The computed translational diffusivities and intrinsic

Crystallization-Induced Fluid Flow in Polymer Melts Undergoing Solidification

February 19, 2007
Author(s)
Donghua Xu, Z G. Wang, Jack F. Douglas
The formation of semi-crystalline plastic polymer materials often occurs under confinement conditions where high pressure imprinting or casting in a mold are involved. To gain insight into this highly non-equilibrium process, we examine the nature of the

Field-Induced Formation of Linear, Mesoscopic Polymer Chains From Ferromagnetic Nanoparticles

February 2, 2007
Author(s)
Jason Benkoski, Steven Bowles, Bryan Korth, Ronald L. Jones, Jack F. Douglas, Alamgir Karim, Jeffrey Pyun
Polymer-coated ferromagnetic colloids are first assembled with an applied magnetic field and then permanently fixed into one-dimensional mesostructures using a novel liquid-liquid interfacial system known as Fossilized Liquid Assembly. Using polystyrene

Pattern-directed to isotropic dewetting transition in polymer films on micropatterned surfaces with differential surface energy contrast

January 27, 2007
Author(s)
D Julthongpiput, Wenhua Zhang, Jack F. Douglas, Alamgir Karim, Michael J. Fasolka
Surface chemical patterns can both cause and direct dewetting in overlying thin films. However, a key factor in this behavior, the magnitude of surface energy differences between pattern domains ( ?g ), is largely unevaluated. To probe the effect of this

Photocurable Oil/Water Interfaces as a Universal Platform for 2-D Self-Assembly

December 14, 2006
Author(s)
Jason Benkoski, Ronald L. Jones, Jack F. Douglas, Alamgir Karim
We present a novel platform for the creation of 2-D assemblies from nanoscale building blocks. The system consists of an oil/water interface in which the oil phase can be flash-cured upon UV exposure. The photopolymerizable material, 1,12-dodecanediol

Characterization of Atomic Motions Governing Grain Boundary Migration

September 24, 2006
Author(s)
Hao Zhang, David J. Srolovitz, Jack F. Douglas, James A. Warren
Molecular dynamics simulations were employed to study atomic motion within stationary and migrating asymmetric tilt grain boundaries. We employ several measures of the complexity of the atomic trajectories, including the van Hove correlation function, the

A Hybrid Finite Element-Analytical Method For Determining the Intrinsic Elastic Moduli of Particles Having Moderately Extended Shapes and a Wide Rande of Elastic Properties

August 1, 2006
Author(s)
Edward J. Garboczi, Jack F. Douglas, Howard Hung
The presence of a low (dilute) concentration of paniculate inclusions having any shape and any property mismatch with the matrix in which they are placed, influences the elasticity of the resulting composite material. This influence is via the intrinsic

Polycrystalline Patterns in Far-From-Equilibrium Freezing: A Phase Field Study

August 1, 2006
Author(s)
L Granasy, T Pusztai, T Borzsonyi, G Toth, G -. Tegze, James A. Warren, Jack F. Douglas
We discuss the formation of polycrystalline microstructures with the framework of phase field theory. First, the model is tested for crystal nucleation in a hard sphere system. It is shown that, when evaluating the model parameters from molecular dynamics

Influence of Confinement on the Fragility of Antiplasticized and Pure Polymer Films

July 27, 2006
Author(s)
Robert A. Riggleman, K Yoshimoto, Jack F. Douglas, J J. de Pablo
We investigate by molecular dynamics simulation how thin film confinementmodifies the fragility of a model glass-forming liquid characterized previously in the bulk. Film confinement is found to reduce the relative fragility of the polymer fluid, leading

Symmetry, Equivalence and Molecular Self-Organization

March 1, 2006
Author(s)
K Van Workum, Jack F. Douglas
Abstract: Self-organization is central to the formation of numerous biological structures and the emulation of this process through the creation of synthetic counterparts offers great promise for nanofabrication. Our approach to understanding the
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