The approach of the elastic continuum limit in small amorphous bodies formed by weakly polydisperse Lennard-Jones beads is investigated a systematic finite-size study. We show that classical elasticity breaks down when wavelength sollicitation smaller than characteristic length approximately 30 molecular sizes. Due to this surprisingly large effect ensembles containing up N=40,000 particles have been required two dimensions yield convincing match with predictions for eigenfrequency spectrum...

Unconcatenated, unknotted polymer rings in the melt are subject to strong interactions with neighboring chains due presence of topological constraints. We study this by computer simulation using bond-fluctuation algorithm for up N=512 statistical segments at a volume fraction \ensuremath{\Phi}=0.5 and show that more compact than Gaussian chains. A careful finite-size analysis average ring size R\ensuremath{\propto}${\mathit{N}}^{\ensuremath{\nu}}$ yields an exponent...

Extending recent numerical studies on two-dimensional amorphous bodies, we characterize the approach of elastic continuum limit in three-dimensional (weakly polydisperse) Lennard-Jones systems. While performing a systematic finite-size analysis (for two different quench protocols), investigate nonaffine displacement field under external strain, linear response to an $\ensuremath{\delta}$ force, and low-frequency harmonic eigenmodes their density distribution. Qualitatively similar behavior...

Using large scale molecular dynamics simulations we investigate the properties of nonaffine displacement field induced by macroscopic uniaxial deformation amorphous silica, a strong glass according to Angell's classification. We demonstrate existence length $\ensuremath{\xi}$ characterizing correlations this (corresponding volume about 1000 atoms), and compare its structure one observed in standard fragile model glass. The ``boson-peak'' anomaly density states can be traced back both cases...

We present a new approach to the modelling of stress propagation in static gran- ular media, focussing on conical sandpile constructed from point source.JOURNAL DE PHYSIQUE I N°1 stresses three-dimensional (conical) pile do not depend much which secondary closure is chosen.Three-dimensional results for FPA model are good semiquantitative agreement with published experimental data piles (including dip); does ex- clude, but nor it support, OSL parameters somewhat different FPA.The strategy we...

We present precise and reproducible mean pressure measurements at the bottom of a cylindrical granular column. If constant overload is added, linear in nonmonotonic column height. The results are {\em quantitatively} consistent with local, relation between stress components, as was recently proposed by some us. They contradict simplest classical (Janssen) approximation, may pose rather severe test competing models.

The scaling of the bond-bond correlation function P1(s) along linear polymer chains is investigated with respect to curvilinear distance s flexible chain and monomer density rho via Monte Carlo molecular dynamics simulations. Surprisingly, correlations in dense three-dimensional solutions are found decay a power law approximately s(-omega) omega=3/2 exponential behavior commonly assumed clearly ruled out for long chains. In semidilute solutions, dependent g(-omega(0))(s/g)(-omega)...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharged diblock copolymers at interfacesJ. Wittmer and J. F. JoannyCite this: Macromolecules 1993, 26, 11, 2691–2697Publication Date (Print):May 1, 1993Publication History Published online1 May 2002Published inissue 1 1993https://doi.org/10.1021/ma00063a009RIGHTS & PERMISSIONSArticle Views341Altmetric-Citations115LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF HTML)...

By means of molecular dynamics simulations and scaling theory we study the response opposing polymer brushes to constant shear motion under good solvent conditions. Model systems that contain explicit molecules (Lennard-Jones dimers) are compared solvent-free while varying distance between grafted layers their parameters, chain length grafting density. Our reveals a power-law dependence macroscopic transport properties on Weissenberg number, W, beyond linear response. For instance, find...

The interplay of topological constraints and the persistence length ring polymers in their own melt is investigated by means dynamical Monte Carlo simulations a three-dimensional lattice model. We ask if results are consistent with an asymptotically regime where rings behave like (compact) animals self-consistent network imposed neighboring rings. Tuning provides efficient route to increase overlap required for this mean-field picture hold: effective Flory exponent size decreases down nu...

We investigate in detail two models describing how stresses propagate and fluctuate granular media. The first one is a scalar model where only the vertical component of stress tensor considered. In continuum limit, this equivalent to diffusion equation (where role time played by coordinate) plus randomly varying convection term. calculate response correlation function discuss several properties, particular related distribution function. then turn tensorial model, basic starting point wave...

The question of the existence a structural glass transition in two dimensions is studied using mode coupling theory (MCT). We determine explicit $d$ dependence memory functional for one-component systems. Applied to we solve MCT equations numerically monodisperse hard disks. A dynamic found at critical packing fraction ${\ensuremath{\varphi}}_{c}^{d=2}\ensuremath{\cong}0.697$ which above ${\ensuremath{\varphi}}_{c}^{d=3}\ensuremath{\cong}0.516$ by about 35%. ${\ensuremath{\varphi}}_{c}^{d}$...

Melts of unconcatenated and unknotted polymer rings are a paradigm for soft matter ruled by topological interactions. We propose description system length N as collection smaller polydisperse Gaussian loops, ranging from the entanglement to skeleton ring , assembled in random trees. Individual melt predicted be marginally compact with mean square radius gyration . As rule, simple power laws asymptotically long come sluggish crossovers. Experiments computer simulations merely deal crossover...

We report results of extensive dynamical Monte Carlo investigations on self-assembled equilibrium polymers (EP) without loops in good solvent. (This is thought to provide a model giant surfactant micelles.) Using novel algorithm we are able describe efficiently both static and dynamic properties systems which the mean chain length 〈L〉 effectively comparable that laboratory experiments (up 5000 monomers, even at high polymer densities). sample up scission energies E/kBT=15 over nearly three...

We discuss the dynamic properties of a semidilute grafted polymer layer exposed to pure solvent. When grafting energy head groups chains is finite, desorb and are expelled from layer. combine Monte Carlo simulations using bond fluctuation model self-consistent mean field calculations scaling analysis. Chain desorption can be seen as two step process. For strongly polymers limiting group. The chain then by osmotic pressure gradient. A cut off wall at constant velocity its center mass....

The linear response of two-dimensional amorphous elastic bodies to an external delta force is determined in analogy with recent experiments on granular aggregates. For the generated forces, stress, and displacement fields, we find strong relative fluctuations order 1 close source, which, however, average out readily classical predictions isotropic continuum elasticity. stress decay (essentially) exponentially distance from source. Only beyond a surprisingly large distance,...

A cornerstone of modern polymer physics is the `Flory ideality hypothesis' which states that a chain in melt adopts `ideal' random-walk-like conformations. Here we revisit theoretically and numerically this pivotal assumption demonstrate there are noticeable deviations from ideality. The come interplay connectivity incompressibility melt, leading to an effective repulsion between segments all sizes $s$. amplitude increases with decreasing $s$ where become more swollen. We illustrate swelling...

The pressure distribution beneath a conical sandpile, created by pouring sand from point source onto rough rigid support, shows pronounced minimum below the apex (‘the dip’). Recent work authors has attempted to explain this phenomenon invoking local rules for stress propagation that depend on geometry, and hence construction history, of medium. We discuss fundamental difference between such approaches, which lead hyperbolic differential equations, elastoplastic models, equations are...

Conformational properties of polymer melts confined between two hard structureless walls are investigated by Monte Carlo simulation the bond-fluctuation model. Parallel and perpendicular components chain extension, bond-bond correlation function structure factor computed compared with recent theoretical approaches attempting to go beyond Flory's Silberberg's hypotheses. We demonstrate that for ultrathin films where thickness, $H$, is smaller than excluded volume screening length (blob size),...

Self-avoiding polymers in strictly two-dimensional (d=2) melts are investigated by means of molecular dynamics simulation a standard bead-spring model with chain lengths ranging up to N=2048. The chains adopt compact configurations typical size R(N)∼Nν ν=1/d. precise measurement various distributions internal distances allows direct test the contact exponents Θ0=3/8, Θ1=1/2, and Θ2=3/4 predicted Duplantier. Due segregation ratio end-to-end distance Re(N) gyration radius Rg(N) becomes...

We revisit the relation between shear-stress relaxation modulus G(t), computed at finite shear strain 0<γ≪1, and autocorrelation functions C(t)|(γ) C(t)|(τ) computed, respectively, imposed γ mean stress τ. Focusing on permanent isotropic spring networks it is shown theoretically computationally that in general G(t)=C(t)|(τ)=C(t)|(γ)+G(eq) for t>0 with G(eq) being static equilibrium modulus. G(t) thus must become different solids impossible to obtain alone from as often assumed. comment...