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Search Publications by: Jack F. Douglas (Assoc)

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Displaying 51 - 75 of 361

Hierarchically Patterned Elastomeric and Thermoplastic Polymer Films through Nanoimprinting and Ultraviolet Light Exposure

November 13, 2018
Author(s)
Jack F. Douglas, Ying Chen, Manish Kulkarni, Allan Marshall, Alamgir Karim, ZiLu Wang, Xiaoteng Wang, Abdullah Al-Enizi, Ahmed Elzatahry, Andrey V. Dobrynin
We develop a simple and generally applicable method to fabricate hierarchical interfacial patterns in elastomer and thermoplastic polymer films through a combination of nanoimprinting and UVO microlithography. Using this method, tunable and hierarchically

Tuning the Relaxation of Nano-Patterned Polymer Films with Polymer-Grafted Nanoparticles: Observation of Entropy-Enthalpy Compensation

November 6, 2018
Author(s)
Sonal Bhadauriya, Xiaoteng Wang, Jack F. Douglas, Praveen Pitliya, Jianan Zhang, Dharmaraj Raghavan, Michael R. Bockstaller, Christopher Stafford, Alamgir Karim
Polymer films provide a versatile "plastic" material in which complex functional relief patterns can be imprinted with a resolution down to tens of nanometers. However, the utility of such patterned materials is limited by the tendency of imprinted

Tuning the Relaxation of Nanopatterned Polymer Films with Polymer-Grafted Nanoparticles: Observation of EntropyEnthalpy Compensation

November 6, 2018
Author(s)
Jack F. Douglas, Xiaoteng Wang, Sonal Bhadauriya, Ren Zhang, Praveen Pitliya, Dharmaraj Raghavan, Alamgir Karim
We show that the previously observed polymeric clustering of nanoparticles (NPs) with grafted chains within polymer matrices can be pattern-directed by nanoimprinting ultrathin nanocomposite films so that the NPs segregate to thicker film regions where

A Comparison Between The Solution Properties of Knotted Ring and Star Polymers

October 31, 2018
Author(s)
Luis F. Vargas Lara, Beatriz Pazmino, Jack F. Douglas
We computationally investigate the solution properties of knotted flexible ring and star polymers by combining molecular dynamics simulation (MD) and path-integral calculations. In particular, we consider knotted rings having a minimal crossing number mc

Complex coacervation in polyelectrolytes from a coarse-grained model

August 22, 2018
Author(s)
Vivek M. Prabhu, Marat Andreev, Jian Qin, Matthew Tirrell, Juan J. de Pablo, Jack F. Douglas
Polyelectrolyte coacervation refers to the formation of distinct liquid phases that arise when polyelectrolytes of opposite charge are mixed under appropriate polymer and salt concentrations. Molecular-level studies of complex polyelectrolyte coacervation

Complex coacervation in polyelectrolytes from a coarse-grained model

August 22, 2018
Author(s)
Jack F. Douglas, Marat Andreev, Juan J. DePablo, Vivek Prabhu, Matthew Tirrell
Polyelectrolyte coacervation refers to the formation of distinct liquid phases that arise when polyelectrolytes are mixed under appropriate polymer and salt concentrations. Molecular-level studies of complex polyelectrolyte coacervation have been limited

Competitive solvation effects in polyelectrolyte solutions

August 1, 2018
Author(s)
Alexandros Chremos, Jack F. Douglas
An understanding of the solution properties and phase behavior of natural and synthetic polyelectrolytes requires an understanding of the competitive association of water (“hydration”) and ion association to the polymer backbone and the consequences of

Polyelectrolyte association and solvation

July 10, 2018
Author(s)
Alexandros Chremos, Jack F. Douglas
There has been significant interest in the tendency of highly charged particles having the same charge to form dynamic clusters in solution, but an accepted theoretical framework that can account for this ubiquitous phenomenon has been slow to develop. The

Structure and Dynamics of a Graphene Melt

May 22, 2018
Author(s)
Jack F. Douglas, Sinan Keten, Fernando Vargas-Lara, Wenjie Xia
We show by molecular dynamics simulation that bulk materials composed of graphene nanosheets exhibit fluid-like properties similar to linear polymer melts at elevated temperatures and that these materials transform into a glassy or “foam” state at low

Energy Renormalization Method for the Coarse-Graining of Polymer Viscoelasticity

May 10, 2018
Author(s)
Jake Song, David D. Hsu, Kenneth R. Shull, Frederick R. Phelan Jr., Jack F. Douglas, Wenjie Xia, Sinan Keten
Developing time and temperature transferable coarse-grained (CG) models is essential for the computational prediction and design of polymeric glass-forming materials, but this goal has remained elusive. The dynamics of CG models are often greatly altered

Influence of Ion Solvation on the Properties of Electrolyte Solutions

April 3, 2018
Author(s)
Marat Andreev, Juan J. DePablo, Alexandros Chremos, Jack F. Douglas
It is widely appreciated that the addition of salts to water leads to significant changes in the thermodynamic and dynamic properties of these aqueous solutions, which have great significance in biology and manufacturing applications. However, no

Weak and Strong Gels and the Emergence of the Amorphous Solid State

February 23, 2018
Author(s)
Jack F. Douglas
Gels are amorphous solids whose macroscopic viscoelastic response derives from contraints in the material that serve to localize the constituent molecules or particles about their average positions in space. These contraints may either be local in nature

Topological Rigidification of Flexible Polymers in Solution

February 22, 2018
Author(s)
Jack F. Douglas, Fernando Vargas-Lara
We use molecular dynamic simulations on a coarse-grained model for flexible polymers in solution to study how molecular topology affects the intrinsic rigidity of polymeric chains. In particular, we study how polymeric "topological complexity", defined by

What Does the Tg of Thin Polymer Films Really Tell Us?

February 22, 2018
Author(s)
Wengang Zhang, Francis W. Starr, Jack F. Douglas
The disparate results for Tg shifts in ultra-thin polymer films with the same film thickness, substrate, and chemistry raises the question of whether Tg is a useful way to characterize thin films. Underlying many Tg measurements is the assumption that Tg

Valence, loop formation and universality in self-assembling patchy particles

February 7, 2018
Author(s)
Debra J. Audus, Francis W. Starr, Jack F. Douglas
Patchy particles have emerged as an attractive model for phase separation and self-assembly in globular proteins solutions, colloidal patchy particles, and molecular fluids where directional interactions are operative. In our previous work, we extensively

Energy Renormalization to Coarse-Graining of the Dynamics of a Model Glass-Forming Liquid

February 5, 2018
Author(s)
Wenjie Xia, Jake Song, Nitin Hansoge, Frederick R. Phelan Jr., Sinan Keten, Jack F. Douglas
Soft condensed matters characteristically exhibit a strong temperature dependence of relaxation properties due to glass formation, but currently no effective temperature transferable coarse- graining method exists that allows for the prediction of their

String-like Collective Motion and Diffusion in the Interfacial Region of Ice

November 20, 2017
Author(s)
Jack F. Douglas, Hao Zhang, Xuhang Tong, Xinyi Wang
We investigate the collective molecular motions and diffusion of water molecules in the mobile interfacial region of the secondary prismatic plane of hexagonal ice by molecular dynamics simulation based on the TIP4P/2005 water potential and metrologies of
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