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Search Publications by: Jack F. Douglas (Assoc)

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Displaying 176 - 200 of 361

Crystallization of Poly(ethylene oxide) on Topographically Patterned Substrates

October 16, 2008
Author(s)
Brian C. Okerberg, Christopher Soles, Jack F. Douglas, Alamgir Karim
Crystallization of poly(ethylene oxide) (PEO) on topographically patterned substrates is investigated. Primary nucleation was dramatically enhanced during solvent drying on patterned substrates compared to flat films. The nucleation density also increased

Dispersion and Shear Viscosity of a Simulated Polymer Nanocomposite

October 16, 2008
Author(s)
Francis W. Starr, Jack F. Douglas, S C. Glotzer
Using molecular dynamics simulations, we explore properties affecting nano-filler dispersion in a dense bead-spring polymer melt, and how the state of dispersion alters the response of the system to shear. We determine a simple metric to determine the

Entanglement Effects on the Dewetting of Polymer Thin Films

October 16, 2008
Author(s)
K A. Barnes, Alamgir Karim, Jack F. Douglas, Da-Wei Liu, Eric J. Amis
We investigate the dewetting of entangled and unentangled polymer films from model viscous polymer and inorganic substrates. Linear and hypergraft polyethyloxazoline (PEOX) polymers are chosen as the unentangled and entangled dewetting fluid, respectively

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
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