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Search Publications by: Jack F. Douglas (Assoc)

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Displaying 126 - 150 of 363

Polymer Glass-Formation in Variable Dimension

January 14, 2016
Author(s)
Jack F. Douglas, Freed Karl, Wensheng Xu
We explore the nature of glass-formation in variable spatial dimensionality (d) based on the generalized entropy theory, a synthesis of the Adam-Gibbs model with direct computation of the configurational entropy of polymer fluids using an established

Cosolvency and cononsolvency explained in terms of a Flory-Huggins type theory

October 7, 2015
Author(s)
Jack F. Douglas, Jacek Dudowicz, Freed Karl
Standard classic Flory-Huggins (FH) theory is employed to describe the enigmatic cosolvency and co-nonsolvency phenomena for systems of polymers dissolved in mixed solvents. In particular, phase boundaries (spinodals) are calculated for solutions of

When does a branched polymer becomes a particle?

September 17, 2015
Author(s)
Alexandros Chremos, Jack F. Douglas
Melts with topologically distinct molecular structures are investigated by molecular dynamics simulation. We determine the mean polymer size and shape, and glass transition temperature for each molecular topology. Both in terms of structure and dynamics

The Osmotic Virial Repersentation of the Free Energy of Polymer Mixing

September 14, 2015
Author(s)
Jack F. Douglas, August W. Bosse
In this Letter we derive a new representation of the free energy of polymer mixing. We begin with a Flory-Huggins-like free energy of mixing, and assume that the excess free energy of mixing exhibits an arbitrary dependence on the blend composition that

Direct Immersion Annealing of Thin Block Copolymer Films

September 9, 2015
Author(s)
Jack F. Douglas, Alamgir Karim, Arvind Arvind Modi1, Sarang Bhaway, Bryan D. Vogt, Abdullah Al-Enizi, Ahmed Elzatahry, Ashutosh Sharma
We demonstrate that direct immersion annealing (DIA) greatly enhances the rate at which block copolymer (BCP) films order into stable morphologies when the BCP films are immersed in carefully selected mixtures of good and marginal solvents that can impart

Dimensional Reduction of Duplex DNA Under Nanofluidic Slit Confinement

August 19, 2015
Author(s)
Luis Fernando Vargas Lara, Jack F. Douglas, Samuel M. Stavis, Elizabeth A. Strychalski, Jon C. Geist, Brian J. Nablo
There has been much recent interest in the dimensional properties of duplex DNA under nanoscale confinement conditions as a problem of fundamental interest in both technological and biological fields. This has led to a series of measurements by

A Unifying Framework to Quantify the Effects of Boundary Stiffness, Polymer-Substrate Interactions and Substrate Roughness on the Dynamics of Thin Supported Polymer Films

June 21, 2015
Author(s)
Jack F. Douglas, Paul Hanakata, Francis W. Starr, Beatriz Betancourt
Changes in the dynamics of supported polymer films in comparison to bulk materials involve a complex convolution of effects, such as boundary thermodynamic interactions, boundary roughness and compliance, in addition to finite film thickness. We consider

Confronting the Complexity of Commercial Carbon Nanotube Materials

May 13, 2015
Author(s)
Luis Fernando Vargas Lara, Jack F. Douglas
The morphology of commercially available carbon nanotube materials is often much more complex than the term “carbon nanotube” (CNT) would imply. Commercial CNT materials are typically composed of roughly spherical CNT domains having a highly ramified

Interplay of particle shape and suspension properties: a study of cube-like particles

March 20, 2015
Author(s)
Debra J. Audus, Ahmed M. Hassan, Edward J. Garboczi, Jack F. Douglas
With advances in anisotropic particle synthesis, particle shape is now a feasible parameter for tuning suspension properties. However, there is a need to determine how these newly synthesized particles affect suspension properties and a need to solve the

Critical Examination of the Colloidal Particle Model of Globular Proteins

February 3, 2015
Author(s)
Prasad S. Sarangapani, Steven D Hudson, Ronald L. Jones, Jack F. Douglas, Jai A. Pathak
Recent studies of globular protein solutions have uniformly adopted a colloidal view of proteins as particles, a perspective that neglects the polymeric primary structure of these biological macromolecules, their intrinsic flexibility and their ability to

The meaning of the universal WLF parameters of glass-forming polymer liquids

January 7, 2015
Author(s)
Jack F. Douglas, Jacek Dudowicz, Karl Freed
Although the Williams-Landell-Ferry (WLF) equation for the segmental relaxation time tau of glass forming materials is one of most commonly encountered relations in polymer physics, the molecular basis for this equation is not well understood. The WLF

Advances in the generalized entropy theory of glass-formation in polymer melts

December 21, 2014
Author(s)
Jack F. Douglas, J Dudowicz, Karl Freed
The generalized entropy theory (GET) of polymeric glass-forming liquids is reformulated in a simpler and more natural formalism than our previous version of this theory. This new theory is then applied to survey essential trends in the dependence of the

Prediction and Validation of Diffusion Coefficients in a Model Drug Delivery System Using Microsecond Atomistic Molecular Dynamics Simulation and Vapor Sorption Analysis

October 21, 2014
Author(s)
Christopher Forrey, D M. Saylor, Joshua S. Silverstein, Jack F. Douglas, Eric Davis, Yossef A. Elabd
Diffusion of small to medium sized molecules in polymeric medical device materials underlies a broad range of public health concerns related to unintended leaching from or uptake into implantable medical devices. Knowledge of diffusion rates is thus
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