Slow knot formation by suppressed self-reptation in a collapsed polymer chain
Mitsuo Nakata, Yoshiki Nakamura, Naoki Sasaki, and Yasuyuki Maki
Chain-expansion processes from knotted globules have been measured for poly(methyl methacrylate) (PMMA) in the mixed solvent tert-butyl alcohol (TBA) + water (2.5 vol %) by static light scattering. The solution was quenched from the Theta temperature of 41.5 C to 37.0 C, aged there for a time period ... [Phys. Rev. E 85, 021802 ] published .
Superensembles of linear viscoelastic models of polymer melts
Sachin Shanbhag, Seung Joon Park, and Zuowei Wang
The idea of incorporating multiple models of linear rheology into a superensemble, to forge a consensus forecast from the individual model predictions, is investigated. The relative importance of the individual models in the so-called multimodel superensemble (MMSE) was inferred by evaluating their ... [J. Rheol. 56, 279 (2012)] published Thu Feb 2, 2012.
Contact percolation transition in athermal particulate systems
Tianqi Shen, Corey S. O'Hern, and M. D. Shattuck
Typical quasistatic compression algorithms for generating jammed packings of purely repulsive, frictionless particles begin with dilute configurations and then apply successive compressions with the relaxation of the elastic energy allowed between each compression step. It is well known that during ... [Phys. Rev. E 85, 011308 ] published .
Acoustic waves excited by phonon decay govern the fracture of brittle materials
Yan Kucherov, Graham Hubler, John Michopoulos, and Brant Johnson
The behavior of brittle materials under ballistic impacts is often associated with failure waves that are producing small fracture particles with a surface area requiring large energy input. Numerous attempts to explain this effect since the 1960s did not yield convincing results. Here we propose th ... [J. Appl. Phys. 111, 023514 (2012)] published Thu Jan 26, 2012.
Simple Model for the Deformation-Induced Relaxation of Glassy Polymers
S. M. Fielding, R. G. Larson, and M. E. Cates
Glassy polymers show strain hardening: at constant extensional load, their flow first accelerates, then arrests. Recent experiments have found this to be accompanied by a striking and unexplained dip in the segmental relaxation time. Here we explain such behavior by combining a minimal model of flow ... [Phys. Rev. Lett. 108, 048301 ] published .
Rheology of Ring Polymer Melts: From Linear Contaminants to Ring-Linear Blends
Jonathan D. Halverson, Gary S. Grest, Alexander Y. Grosberg, and Kurt Kremer
Ring polymers remain a challenge to our understanding of polymer dynamics. Experiments are difficult to interpret because of the uncertainty in the purity and dispersity of the sample. Using both equilibrium and nonequilibrium molecular dynamics simulations we have investigated the structure, dynami ... [Phys. Rev. Lett. 108, 038301 ] published .
Active Nonlinear Microrheology in a Glass-Forming Yukawa Fluid
D. Winter, J. Horbach, P. Virnau, and K. Binder
A molecular dynamics computer simulation of a glass-forming Yukawa mixture is used to study the anisotropic dynamics of a single particle pulled by a constant force. Beyond linear response, a scaling regime is found where a force-temperature superposition principle of a Peclet number holds. In the l ... [Phys. Rev. Lett. 108, 028303 ] published .
Shear Banding in Molecular Dynamics of Polymer Melts
Jing Cao and Alexei E. Likhtman
In order to establish constitutive equations for a viscoelastic fluid uniform shear flow is usually required. However, in the last 10 years S. Q. Wang and co-workers have demonstrated that some entangled polymers do not flow with the uniform shear rate as usually assumed, but instead choose to separ ... [Phys. Rev. Lett. 108, 028302 ] published .
Dynamics on the Laminar-Turbulent Boundary and the Origin of the Maximum Drag Reduction Asymptote
Li Xi and Michael D. Graham
Dynamical trajectories on the boundary in state space between laminar and turbulent plane channel flowedge statesare computed for Newtonian and viscoelastic fluids. Viscoelasticity has a negligible effect on the properties of these solutions, and, at least at a low Reynolds number, their mean veloci ... [Phys. Rev. Lett. 108, 028301 ] published .
Defect modeling in spreading nematic droplets
T.-S. Lin, L. Kondic, and L. J. Cummings
Experiments by Poulard and Cazabat [Langmuir 21, 6270 (2005)] on spreading droplets of nematic liquid crystal (NLC) reveal a surprisingly rich variety of behavior, including at least two different emerging length scales resulting from a contact line instability. In earlier work [Cummings, Lin, and K ... [Phys. Rev. E 85, 012702 ] published .
Dynamics in dense hard-sphere colloidal suspensions
Davide Orsi, Andrei Fluerasu, Abdellatif Moussaid, Federico Zontone, Luigi Cristofolini et al.
The dynamic behavior of a hard-sphere colloidal suspension was studied by x-ray photon correlation spectroscopy and small-angle x-ray scattering over a wide range of particle volume fractions. The short-time mobility of the particles was found to be smaller than that of free particles even at relati ... [Phys. Rev. E 85, 011402 ] published .
Fluid dynamics of dilatant fluids
Hiizu Nakanishi, Shin-ichiro Nagahiro, and Namiko Mitarai
A dense mixture of granules and liquid often shows a severe shear thickening and is called a dilatant fluid. We construct a fluid dynamics model for the dilatant fluid by introducing a phenomenological state variable for a local state of dispersed particles. With simple assumptions for an equation o ... [Phys. Rev. E 85, 011401 ] published .
Steady Couette flows of elastoviscoplastic fluids are nonunique
I. Cheddadi, P. Saramito, and F. Graner
The HerschelBulkley rheological fluid model includes terms representing viscosity and plasticity. In this classical model, below the yield stress the material is strictly rigid. Complementing this model by including elastic behavior below the yield stress leads to a description of an elastoviscoplas ... [J. Rheol. 56, 213 (2012)] published Fri Jan 13, 2012.
Comparison of the kinetic friction of planar neutral and polyelectrolyte polymer brushes using molecular dynamics simulations
Yangpeng Ou, Jeffrey B. Sokoloff, and Mark J. Stevens
We have simulated the relative shear motion of both neutral and polyelectrolyte end-grafted polymer brushes using molecular dynamics. The flexible neutral polymer brush is treated as a bead-spring model, and the polyelectrolyte brush is treated the same way except that each bead is charged and there ... [Phys. Rev. E 85, 011801 ] published .
Mechanism of spontaneous hole formation in thin polymeric films
Kaijia Yu, Henrik Koblitz Rasmussen, Jose Manuel Roman Marin, and Ole Hassager
We show computationally that (molten) thin polymeric film containing nonequilibrium configurations originating from a solvent evaporation may develop holes spontaneously in the molten state, and that they appear delayed. Polymers above the glass transition temperature are liquids where the flow depe ... [Phys. Rev. B 85, 024201 ] published .
ABOUT MECHANICAL STRENGTH OF POROUS MATERIALS
Petru Ciobanu
It is known that the presence of the pores influences the mechanical strength of porous materials. The author of this scientific report has recently created and published a new model for calculating the effective stresses of cohesive, porous and cracked rocks. Starting from this model he obtained a ... [AIP Conf. Proc. 1400, 453 (2011)] published Wed Dec 28, 2011.
Self-assembled organic channel/polymer dielectric layer for organic thin-film transistor applications
Ji Hoon Park, Kwang H. Lee, Sung-jin Mun, Gunwoo Ko, S. Heo et al.
We report on the solution-processed thin-film transistors (TFTs) fabricated by the vertical flowing of the viscous 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) and isotatic (i-) poly-(methyl methacrylate) (PMMA) blend. This vertical flowing method provide us with phase-separated fil ... [AIP Conf. Proc. 1399, 847 (2011)] published Wed Dec 28, 2011.
Thermal Jamming of a Colloidal Glass
Praveen Agarwal, Samanvaya Srivastava, and Lynden A. Archer
We investigate the effect of temperature on structure and dynamics of a colloidal glass created by tethering polymers to the surface of inorganic nanoparticles. Contrary to the conventional assumption, an increase in temperature slows down glassy dynamics of the material, yet causes no change in its ... [Phys. Rev. Lett. 107, 268302 ] published .
Boundary effect in electrorheological fluids
X. L. Gong, F. Yang, S. H. Xuan, L. H. Zong, W. Zhu et al.
The effect of the boundary friction coefficient on the rheological properties of the electrorheological (ER) fluids in quasistatic and dynamic states is investigated by computer simulation. The relation between the shear stress and the boundary friction coefficient in quasistatic and dynamic states ... [Phys. Rev. E 84, 061505 ] published .
Criterion for Extensional Necking Instability in Polymeric Fluids
Suzanne M. Fielding
We study the linear instability with respect to necking of a filament of polymeric fluid undergoing uniaxial extension. Contrary to the widely discussed Considere criterion, we find the onset of instability to relate closely to the onset of downward curvature in the time (and so strain) evolution of ... [Phys. Rev. Lett. 107, 258301 ] published .
Molecular Dynamics Simulation of Binary Fluid in a Nanochannel
Shanta Mullick, Y. Pathania, and P. K. Ahluwalia
This paper presents the results from a molecular dynamics simulation of binary fluid (mixture of argon and krypton) in the nanochannel flow. The computational software LAMMPS is used for carrying out the molecular dynamics simulations. Binary fluids of argon and krypton with varying concentration of ... [AIP Conf. Proc. 1393, 87 (2011)] published Mon Dec 12, 2011.