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Displaying 1351 - 1375 of 1923

Certification of Standard Reference Material 1476a, a Polyethylene Resin

November 29, 2007
Author(s)
Kathleen M. Flynn, S Wetzel, William R. Blair, J R. Maurey
The melt flow rate of Standard Reference Material (SRM) 1476a Branched Polyethylene Resin was determined to be 1.23g/10 min at 190 C under a load of 2.16 kg using the ASTM Method D1238-03, method A. The average results from 30 determinations yielded a

Microdomain Ordering in Laterally Confined Block Copolymer Thin Films

November 29, 2007
Author(s)
August W. Bosse, Carlos Garcia-Cervera, Glenn Fredrickson
We examine the effects of small-scale, hexagonal, lateral confinement on microdomain ordering in $AB$ diblock copolymer thin films using self-consistent field theory (SCFT) simulations. Specifically, we examine a hexagonal confinement well with side length

Characterizing Polymer Brushes via Surface Wrinkling

November 21, 2007
Author(s)
Heqing Huang, Jun Y. Chung, Adam J. Nolte, Christopher M. Stafford
We present the application of surface wrinkling to measure the properties of polymer brush layers tethered to the surface of a deformable silicone substrate. It is demonstrated that the wavelength of the wrinkling pattern linearly increases with the length

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

Combinatorial Polymer Scaffold Libraries

November 1, 2007
Author(s)
Carl G. Simon Jr., J S. Stephens, Matthew Becker
We have developed a method for fabricating combinatorial libraries of porous, three-dimensional, salt-leached, polymer scaffolds that can be used for screening the effect of scaffold properties on cell response. Syringe pumps, tubing and a static mixer are

Critical Role of Side-Chain Attachment Density on the Order and Device Performance of Polythiophenes

October 30, 2007
Author(s)
Regis J. Kline, Dean DeLongchamp, Daniel A. Fischer, Eric K. Lin, Lee J. Richter, Michael L. Chabinyc, Martin Heeney, Iain McCulloch
High performance, solution processable semiconductors are critical to the realization of low cost, large area electronics. We show that a signature molecular packing motif - side-chain interdigitation - correlates to high performance for a large and

The Molecular Origin of Enhanced Toughness in Double-Network Hydrogels

October 22, 2007
Author(s)
Taiki Tominaga, Vijay Tirumala, Eric K. Lin, Jian P. Gong, Hidemitsu Furukawa, Yoshihito Osada, Wen-Li Wu
The long-standing pursuit of a synthetic equivalent to tissue cartilage has seen significant new activity with the development of a new materials strategy: double-network hydrogels (DN-gels) prepared from a combination of an anionic polyelectrolyte and a

Dynamics of Confined Polymer Films Measured via Thermal Wrinkling

October 19, 2007
Author(s)
Kirt A. Page, Derek L. Patton, Rui Huang, Christopher Stafford
In the past several years there have been a number of advances in the understanding of the physics of polymer thin films. However, there still remains a wide range of opportunities to further this understanding through the development of measurement tools

Measurement of Reactivity Ratios in Surface-Initiated Copolymerization

August 21, 2007
Author(s)
Derek L. Patton, Kirt A. Page, Chang Xu, Kirsten Genson, Michael J. Fasolka, Kathryn L. Beers
This work describes a new approach to measure monomer reactivity ratios from surface-initiated copolymerizations using x-ray photoelectron spectroscopy. Styrene/methyl methacrylate statistical copolymer brushes were prepared from various monomer feeds by

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

Microfluidic Dynamic Light Scattering Used for High Throughput Measurements

July 10, 2007
Author(s)
Thomas Q. Chastek, Kathryn L. Beers, Eric J. Amis
When diluted in some solvents, surfactants and block copolymers self-assemble into micelles or vesicles of about 10-100 nm in size. There is a great deal of interest in micelles and vesicles because they are widely used in the formulations industry, and

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

An Apparatus For Folding Yarns And Woven Fabrics Of Ballistic Fibers

June 4, 2007
Author(s)
Walter G. McDonough, Jae Hyun Kim, Nolan J. Brandenburg, William R. Blair, Gale A. Holmes
Folding of ballistic fibers comprising soft body armor may be a factor in the performance deterioration that has been observed in used soft body armor. To quantify the impact of this mechanism, an apparatus was designed and built to simulate the folding

Numerical Optimization of Matrix-Assisted Laser Desorption/Ionization Time-of- Flight Mass Spectrometry: Application to Synthetic Polymer Molecular Mass Distribution Measurement

May 26, 2007
Author(s)
William E. Wallace, Charles M. Guttman, Kathleen M. Flynn, Anthony J. Kearsley
A novel approach is described for the selection of optimal instrument parameters that yield a mass spectrum which best replicates the molecular mass distribution of a synthetic polymer. The application of implicit filtering algorithms is shown to be a

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
Displaying 1351 - 1375 of 1923
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