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Search Publications by: Jack F. Douglas (Fed)

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Displaying 1 - 25 of 355

Dielectric Characterization of H2O and CO2 Uptake by Polyethylenimine Films

April 10, 2024
Jan Obrzut, Jennifer Clark, Avery Baumann, Jack F. Douglas
This study investigates the dielectric properties of branched polyethylenimine (PEI) films in relation to their interaction with moisture and CO2. The dielectric measurements were carried out using a non-contact resonant microwave cavity testing method

A quantitative theoretical model of the boson peak based on stringlet excitations

July 24, 2023
Jack F. Douglas, Cunyuan Jiang, Matteo Baggioli
The boson peak (BP), a low-energy excess in the vibrational density of states over the phonon Debye contribution, is usually identified as one of the distinguishing features between ordered crystals and amorphous solid materials. Despite decades of efforts

Prestress in Composite Polymer Gels as a Model for Articular Cartilage

November 2, 2022
Alexandros Chremos, Jack F. Douglas, Peter Basser, Ferenc Horkay
Articular cartilage is a composite gel-like material found in animal and human joints and exhibits a unique load-bearing performance that has been challenging to reproduce in synthetic materials and in molecular dynamics simulations. We investigate a

Effects of Aspect Ratio of Multi-Walled Carbon Nanotube on Flammability Properties of Polymer Nanocomposites

October 12, 2021
Bani Cipiriano, Takashi Kashiwagi, Srinivasa R. Raghavan, Ying Yang, E A. Grulke, Kazuya Yamammoto, John R. Shields, Jack F. Douglas
The effects of the aspect ratio of multi-walled carbon nanotube (MWNT) on viscoelastic properties and flammability properties of PS/MWNT nanocomposites are studied with two different MWNTs having average aspect ratios of 49 and 150. While no significant

Fluctuation Effects on Surface Pattern Formation in Thin Block Copolymer Films

October 12, 2021
A C. Smith, Jack F. Douglas, Eric J. Amis, Alamgir Karim
Hole formation on the surface of thin block copolymer films is investigated as a function of time (t), temperature (T) and film thickness. The size of the holes, h s, approaches a steady state value at long times h s,∞ = h s(t -> ∞) and we introduce a

Laser Based Angle-Resolved Photoemission, the Sudden Approximation and Quasiparticle-Like Spectral Peaks in Bi 2 Sr 2 Cu 2 O 8 +D

October 12, 2021
j D. Koralek, Jack F. Douglas, N C. Plumb, Z Sun, A V. Fedorov, M M. Murnane, H C. Kapteyn, Steven T. Cundiff, Y Aiura, K Oka, H. Eisaki, D S. Dessau
A new low photon energy regime of angle-resolved photoemission spectroscopy is accessed with lasers and used to study the hight T c superconductor Bid2^CaCu 2O 8d+^delta. The low energy increases bulk sensitivity, reduces background, and improves

Model for Dispersion Rheology

October 12, 2021
J Bicerano, Jack F. Douglas, D A. Brune
A general model of the viscosity of complex-shaped particle dispersions is developed based on an exact virial expansion about the low concentration limit and a mathematical analogy between the hydrodynamics of concentrated particle suspensions and the

Polycrystalline Growth: Dirt Versus Dynamical Heterogeneity

October 12, 2021
L Granasy, T Pusztai, T Borzsonyi, James A. Warren, Jack F. Douglas
Most research into microstructure formation during solidification has focused on single crystal growth forms, ranging from faceted crystals to dendritic growth patterns. However, these growth forms can be peturbed by heterogeneities yielding a rich variety

Temperature Effects on Surface Pattern Formation in Thin Block Copolymer Films

October 12, 2021
A P. Smith, Jack F. Douglas, Eric J. Amis, Alamgir Karim
Hole formation on the surface of thin films of symmetric diblock copolymers is investigated as a function of time, t, temperature, T, and film thickness, h. The size of the holes approaches a steady state value at long times and their long-time size is

Tuning the Fragility of Polymer Melts With Antiplasticizer Additives

October 12, 2021
Robert A. Riggleman, K Yoshimoto, Jack F. Douglas, J J. de Pablo
Using molecular dynamics simulations, we have developed and analyzed a model that exhibits antiplasticization behavior by decreasing the glass transition temperature, increasing the density of the system below the glass transition temperature of the pure

Structure and Dynamics of Star Polymer Films from Coarse-Grained Molecular Simulations

October 5, 2021
Jack F. Douglas, Wengang Zhang, Francis W. Starr, Alexandros Chremos
We quantify the structure and dynamics in molecular simulations of star polymer films of varying arm mass Ma and number of star arms f on a supporting solid substrate with an attractive interaction and compare to the corresponding properties of thin films

Late Stage Domain Coarsening Dynamics of Lamellar Block Copolymers

May 26, 2021
Jack F. Douglas, Maninderjeet Singh, Wenjie Wu, Vinay Nuka, Joseph Strzalka, Alamgir Karim
Block copolymer (BCP) phase separation is an intriguing phenomenon whose dynamics can be expected to differ significantly from that of the polymer blends due to constraint of chain connectivity that limits the ultimate scale of phase separation and the

Why Polymer Glasses with Enhanced Sub-nanosecond Relaxation are Tougher

February 12, 2021
Christopher Soles, Adam B. Burns, Kanae N. Ito, Jack F. Douglas, Robert Dimeo, Madhusudan (Madhu) Tyagi, Jingsheng Wu, Albert F. Yee, Yueh-Ting Shih, Liping Huang
This manuscript explores the connection between the fast relaxation processes in a polymer glass and essential trends in the mechanical toughness, a non-linear mechanical property that is of practical interest for engineering polymers with high impact