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Search Publications by: Jack F. Douglas (Fed)

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Displaying 151 - 175 of 355

NMR Characterization of the Formation Kinetics and Structure of Di-O-Benzylidene Sorbitol Gels Self-Assembled in Organic Solvents

January 19, 2011
Author(s)
David L. VanderHart, Jack F. Douglas, Steven Hudson, Joseph M. Antonucci, Elizabeth A. Wilder
The molecule 1,3:2,4-Di-O-Benzylidene sorbitol (DBS) is a common gelator that forms thermally reversible gels in diverse organic solvents. Solid state 13C and proton NMR techniques, along with electron microscopy, are utilized in an exploratory study of

Stability and Surface Topography Evolution in Nanoimprinted Polymer Patterns under a Thermal Gradient

September 16, 2010
Author(s)
Christopher Soles, Yifu Ding, H. Jerry Qi, Kyle J. Alvine, Hyun W. Ro, Dae Up Ahn, Jack F. Douglas, Sheng Lin-Gibson
Nanostructures created in polymer films by nanoimprint lithography are subject to large stresses, both those from the imprinting processes as well as stresses arising from the intrinsic thermodynamic instabilities. These stresses can induce nanostructure

Wrinkling and Strain Softening in Single-Wall Carbon Nanotube Membranes

March 26, 2010
Author(s)
Erik K. Hobbie, Daneesh O. Simien, Jeffrey A. Fagan, JiYeon Huh, Jun Y. Chung, Steven D. Hudson, Jan Obrzut, Jack F. Douglas, Christopher M. Stafford
Ultrathin layers of single-wall carbon nanotubes (SWCNTs) show considerable promise for applications ranging from fuel-cell membranes and biochemical sensors to bioactive films and transparent electrodes. The high conductivity and extreme anisotropy of

Solvent Retention In Thin Spin-Coated Polystyrene And Poly(Methyl Methacrylate) Homopolymer Films Studied By Neutron Reflectometry

January 19, 2010
Author(s)
Xiaohua Zhang, Kevin G. Yager, Shuhui Kang, Nathaniel J. Fredin, Bulent Akgun, Sushil K. Satija, Jack F. Douglas, Alamgir Karim, Ronald L. Jones
We utilize neutron reflectometry (NR) to probe the amount of residual solvent inside thin polystyrene (PS) and poly(methyl methacrylate) (PMMA) films spin-coated from deuterated toluene polymer solutions onto silicon substrates . The effect of thermal

Interaction of Gold Nanoparticles with Common Human Blood Proteins

December 18, 2009
Author(s)
Silvia H. De Paoli Lacerda, Jung J. Park, Curtis W. Meuse, Denis Pristinski, Matthew Becker, Jack F. Douglas
Gold nanoparticles (NPs) provide a promising platform for diagnostics and therapy, as well as other biomedical applications. The recent literature, however, contains conflicting data regarding the cytotoxicity of NPs. We have thus performed an array of

Capillary Instability in Nanoimprinted Polymer Films

May 21, 2009
Author(s)
Kyle J. Alvine, Yifu Ding, Hyun Wook Ro, Brian C. Okerberg, Alamgir Karim, Christopher L. Soles, Jack F. Douglas
Capillary forces play an active role in defining the equilibrium structure of nanoscale structures. This effect can be especially pronounced in soft materials such as polymers near or above their glass transition temperatures where material flow is

Grain boundaries exhibit the dynamics of glass-forming liquids

May 12, 2009
Author(s)
James A. Warren, Jack F. Douglas, Xuhang Tong, David J. Srolovitz
Polycrystalline materials are composites of crystalline particles or grains separated by thin amorphous grain boundaries (GBs). Although GBs have been exhaustively investigated at low temperatures, at which these regions are relatively ordered, much less

Equilibrium Polymerization Models of Reentrant Self-Assembly

April 24, 2009
Author(s)
Jacek Dudowicz, Jack F. Douglas, Karl Freed
As is well known, liquid-liquid phase separation can occur either upon heating or cooling, corresponding to lower and upper critical solution phase boundaries, respectively. Likewise, self-assembly transitions from a monomeric state to an organized

Dielectric Spectroscopy Investigation of Relaxation in C60-Polyisoprene Nanocomposites

March 23, 2009
Author(s)
Yifu Ding, Sebastian Pawlus, Alexei Sokolov, Jack F. Douglas, Alamgir Karim, Christopher Soles
We investigate the influence of adding C60 nanoparticles on the dielectric relaxation spectra of both unentangled and entangled polyisoprene (PIP). Relaxation modes corresponding to both segmental and chain relaxation were analyzed over a broad temperature

Competition Between Self-Assembly and Surface Adsorption

February 25, 2009
Author(s)
Jacek Dudowicz, Jack F. Douglas, Karl Freed
We investigate a minimal equilibrium polymerization model of the general competition between self-assembly on a boundary and in solution that arises when an assembling system is near a boundary. Adsorption generally occurs upon cooling, but assembly

Particle Motion During the Compaction of Granular Matter

December 19, 2008
Author(s)
Steven Slotterback, Masahiro Toiya, Leonard Goff, Jack F. Douglas, Wolfgang Losert
We track particle motions in a granular material subjected to compaction using a laser scattering based imaging method where compaction is achieved through thermal cycling. Particle displacements in this jammed fluid correlate strongly with rearrangments

Self-Assembly in a Polymer Matrix and its Impact on Phase Separation

November 11, 2008
Author(s)
Jack F. Douglas, Jacek Dudowicz, Karl Freed
Molecular self-assembly often occurs in the presence of long chain polymers, and we develop a theory to describe the competition between self-assembly and phase separation that gen- erally occurs in these complex uids. The theory includes a description of

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