The gyration radius distribution of two‐dimensional polymer chains in a good solvent

1990 ◽  
Vol 92 (2) ◽  
pp. 1362-1364 ◽  
Author(s):  
J. M. Victor ◽  
D. Lhuillier
Keyword(s):  
Polymer Chains ◽  
Gyration Radius ◽  
Two Dimensional

scholarly journals A mechanism for oscillatory instability in viscoelastic cross-slot flow

2009 ◽  
Vol 622 ◽  
pp. 145-165 ◽  
Author(s):  
LI XI ◽  
MICHAEL D. GRAHAM
Keyword(s):  
Reynolds Number ◽  
Stagnation Point ◽  
Low Reynolds Number ◽  
Polymer Processing ◽  
Weissenberg Number ◽  
Polymer Chains ◽  
Oscillatory Instability ◽  
Viscoelastic Flow ◽  
Two Dimensional ◽  
Viscoelastic Liquids

Interior stagnation-point flows of viscoelastic liquids arise in a wide variety of applications including extensional viscometry, polymer processing and microfluidics. Experimentally, these flows have long been known to exhibit instabilities, but the mechanisms underlying them have not previously been elucidated. We computationally demonstrate the existence of a supercritical oscillatory instability of low-Reynolds-number viscoelastic flow in a two-dimensional cross-slot geometry. The fluctuations are closely associated with the ‘birefringent strand’ of highly stretched polymer chains associated with the outflow from the stagnation point at high Weissenberg number. Additionally, we describe the mechanism of instability, which arises from the coupling of flow with extensional stresses and their steep gradients in the stagnation-point region.

scholarly journals Molecular structure of azobenzene-containing systems from classical MD simulations

2015 ◽  
Author(s):  
Olga Guskova ◽  
Vladimir Toshchevikov ◽  
Jaroslav Ilnytskyi ◽  
Marina Saphiannikova
Keyword(s):  
Molecular Structure ◽  
Conformational Changes ◽  
Md Simulations ◽  
Chem Phys ◽  
Polymer Chains ◽  
Gyration Radius ◽  
Light Illumination ◽  
Molecular Glasses ◽  
Mesoscopic Level ◽  
Dynamics Simulations

Azobenzene-containing side chain polymers [1,2] and molecular glasses based on propeller-like C3-symmetric azobenzene mesogenes [3] are investigated in classical molecular dynamics simulations. Two length scales are considered: (i) the molecular level with atomistic resolution, where reversible conformational changes of azobenzene chromophores upon light illumination lead to contractions/extensions of low amplitudes due to a limited size of mesogene groups, and (ii) the mesoscopic level, where light-induced molecular movements are observed over larger distances, comparable with the gyration radius of polymer chains. The influence of isomerization and orientation mechanisms on molecular structure and light-induced deformation is elucidated. [1] J. Ilnytskyi et al., J. Chem. Phys. 135, 044901 (2011). [2] M Saphiannikova et al., Proceedings of SPIE "Optical Materials and Biomaterials in Security and Defence Systems Technology X", 8901, 890138 (2013). [3] N.S. Jadavalli et al., Appl. Phys. Lett. 105, 051601 (2014).

THE HELIX-COIL TRANSITION IN A DOUBLE-STRANDED POLYNUCLEOTIDE AND THE TWO-DIMENSIONAL RANDOM WALK

2012 ◽  
Vol 26 (13) ◽  
pp. 1250083
Author(s):  
G. N. HAYRAPETYAN ◽  
V. F. MOROZOV ◽  
V. V. PAPOYAN ◽  
S. S. POGHOSYAN ◽  
V. B. PRIEZZHEV
Keyword(s):  
Random Walk ◽  
Hydrogen Bonds ◽  
Polymer Chains ◽  
Square Lattice ◽  
Two Dimensional ◽  
Competing Interactions ◽  
New Approach ◽  
Rich Phase ◽  
Coil Transition ◽  
The Rich

The helix-coil transition in a double-stranded homopolynucleotide is considered. The new approach to the melted loops account is proposed. The relative distance between the corresponding monomers of two polymer chains is modeled by the two-dimensional random walk on the square lattice. Returns of the random walk to the origin describe the formation of hydrogen bonds between complementary units. To take into account the interaction of monomers inside the chains, we consider various regimes of return to the origin. One of them involves two competing interactions and demonstrates a nontrivial sharp denaturation transition. The rich phase behavior of the double-stranded homopolynucleotide is discussed in terms of the proposed approach.

Magnetic field controlled behavior of magnetic gels studied using particle-based simulations

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Rudolf Weeber ◽  
Patrick Kreissl ◽  
Christian Holm
Keyword(s):  
Magnetic Particles ◽  
Ac Susceptibility ◽  
Thermal Fluctuations ◽  
Polymer Chains ◽  
Soft Magnetic Materials ◽  
Magnetic Interactions ◽  
Qualitative Behavior ◽  
Homogeneous Field ◽  
Two Dimensional ◽  
Dimensional Models

Abstract This contribution provides an overview of the study of soft magnetic materials using particle-based simulation models. We focus in particular on systems where thermal fluctuations are important. As a basis for further discussion, we first describe two-dimensional models which demonstrate two deformation mechanisms of magnetic gels in a homogeneous field. One is based on the change of magnetic interactions between magnetic particles as a response to an external field; the other is the result of magnetically blocked particles acting as cross-linkers. Based on the qualitative behavior directly observable in the two-dimensional models, we extend our description to three-dimensions. We begin with particle-cross-linked gels, as for those, our three-dimensional model also includes explicitly resolved polymer chains. Here, the polymer chains are represented by entropic springs, and the deformation of the gel is the result of the interaction between magnetic particles. We use this model to examine the influence of the magnetic spatial configuration of magnetic particles (uniaxial or isotropic) on the gel’s magnetomechanical behavior. A further part of the article will be dedicated to scale-bridging approaches such as systematic coarse-graining and models located at the boundary between particle-based and continuum modeling. We will conclude our article with a discussion of recent results for modeling time-dependent phenomena in magnetic-polymer composites. The discussion will be focused on a simulation model suitable for obtaining AC-susceptibility spectra for dilute ferrofluids including hydrodynamic interactions. This model will be the basis for studying the signature of particle–polymer coupling in magnetic hybrid materials. In the long run, we aim to compare material properties probed locally via the AC-susceptibility spectra to elastic moduli obtained for the system at a global level.

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