scholarly journals Contour length fluctuations and constraint release in entangled polymers: Slip-spring simulations and their implications for binary blend rheology

2018 ◽  
Vol 62 (4) ◽  
pp. 1017-1036 ◽  
Author(s):  
Daniel J. Read ◽  
Maksim E. Shivokhin ◽  
Alexei E. Likhtman
Keyword(s):  
Contour Length ◽  
Binary Blend ◽  
Entangled Polymers ◽  
Constraint Release

scholarly journals Comparative Analysis of Different Tube Models for Linear Rheology of Monodisperse Linear Entangled Polymers

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 754 ◽  
Author(s):  
Volha Shchetnikava ◽  
Johan Slot ◽  
Evelyne van Ruymbeke
Keyword(s):  
Experimental Data ◽  
Comparative Analysis ◽  
Hierarchical Model ◽  
Linear Viscoelasticity ◽  
Star Polymers ◽  
Contour Length ◽  
Large Set ◽  
Linear Polymers ◽  
Entangled Polymers ◽  
Constraint Release

The aim of the present paper is to analyse the differences between tube-based models which are widely used for predicting the linear viscoelasticity of monodisperse linear polymers, in comparison to a large set of experimental data. The following models are examined: Milner–McLeish, Likhtman–McLeish, the Hierarchical model proposed by the group of Larson, the BoB model of Das and Read, and the TMA model proposed by the group of van Ruymbeke. This comparison allows us to highlight and discuss important questions related to the relaxation of entangled polymers, such as the importance of the contour-length fluctuations (CLF) process and how it affects the reptation mechanism, or the contribution of the constraint release (CR) process on the motion of the chains. In particular, it allows us to point out important approximations, inherent in some models, which result in an overestimation of the effect of CLF on the reptation time. On the contrary, by validating the TMA model against experimental data, we show that this effect is underestimated in TMA. Therefore, in order to obtain accurate predictions, a novel modification to the TMA model is proposed. Our current work is a continuation of earlier research (Shchetnikava et al., 2014), where a similar analysis is performed on well-defined star polymers.

scholarly journals Contraction of Entangled Polymers After Large Step Shear Deformations in Slip-Link Simulations

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 370 ◽  
Author(s):  
Yuichi Masubuchi
Keyword(s):  
Dynamics Simulation ◽  
Uniaxial Deformation ◽  
Single Chain ◽  
Orientational Relaxation ◽  
Entangled Polymers ◽  
Constraint Release ◽  
Large Step ◽  
Entangled Polymer ◽  
Convective Constraint Release ◽  
Chain Contraction

Although the tube framework has achieved remarkable success to describe entangled polymer dynamics, the chain motion assumed in tube theories is still a matter of discussion. Recently, Xu et al. [ACS Macro Lett. 2018, 7, 190–195] performed a molecular dynamics simulation for entangled bead-spring chains under a step uniaxial deformation and reported that the relaxation of gyration radii cannot be reproduced by the elaborated single-chain tube model called GLaMM. On the basis of this result, they criticized the tube framework, in which it is assumed that the chain contraction occurs after the deformation before the orientational relaxation. In the present study, as a test of their argument, two different slip-link simulations developed by Doi and Takimoto and by Masubuchi et al. were performed and compared to the results of Xu et al. In spite of the modeling being based on the tube framework, the slip-link simulations excellently reproduced the bead-spring simulation result. Besides, the chain contraction was observed in the simulations as with the tube picture. The obtained results imply that the bead-spring results are within the scope of the tube framework whereas the failure of the GLaMM model is possibly due to the homogeneous assumption along the chain for the fluctuations induced by convective constraint release.

Entangled Polymers: Constraint Release, Mean Paths, and Tube Bending Energy

2008 ◽  
Vol 41 (18) ◽  
pp. 6843-6853 ◽  
Author(s):  
D. J. Read ◽  
K. Jagannathan ◽  
A. E. Likhtman
Keyword(s):  
Tube Bending ◽  
Bending Energy ◽  
Entangled Polymers ◽  
Constraint Release

scholarly journals Slip-spring simulations of different constraint release environments for linear polymer chains

2020 ◽  
Vol 7 (3) ◽  
pp. 191046
Author(s):  
Teng Ma ◽  
Guochang Lin ◽  
Huifeng Tan
Keyword(s):  
Relaxation Function ◽  
Polymer Chains ◽  
Contour Length ◽  
Viscoelastic Relaxation ◽  
Relaxation Behaviour ◽  
Experiment Data ◽  
Relaxation Data ◽  
Polymer Relaxation ◽  
Constraint Release ◽  
Good Agreement

The constraint release (CR) mechanism has important effects on polymer relaxation and the chains will show different relaxation behaviour in conditions of monodisperse, bidisperse and other topological environments. By comparing relaxation data of linear polyisoprene (PI) chains dissolved in very long matrix and monodisperse melts, Matsumiya et al. showed that CR mechanism accelerates both dielectric and viscoelastic relaxation (Matsumiya et al. 2013 Macromolecules 46 , 6067. ( doi:10.1021/ma400606n )). In this work, the experimental data reported by Matsumiya et al. are reproduced using the single slip-spring (SSp) model and the CR accelerating effects on both dielectric and viscoelastic relaxation are validated by simulations. This effect on viscoelastic relaxation is more pronounced. The coincidence for end-to-end relaxation and the viscoelastic relaxation has also been checked using probe version SSp model. A variant of SSp with each entanglement assigning a characteristic lifetime is also proposed to simulate various CR environment flexibly. Using this lifetime version SSp model, the correct relaxation function can be obtained with equal numbers of entanglement destructions by CR and reptation/contour length fluctuation (CLF) for monodisperse melts. Good agreement with published experiment data is also obtained for bidisperse melts, which validates the ability to correctly describe the CR environment of the lifetime version model.

Studies of Circular DNA Using a New Electron Microscopic Technique

1973 ◽  
Vol 31 ◽  
pp. 596-597
Author(s):  
C. N. Gordon
Keyword(s):  
Electron Microscopy ◽  
Aqueous Salt Solution ◽  
Contour Length ◽  
Cleavage Surface ◽  
Mica Substrate ◽  
Electron Microscopic ◽  
Replica Technique ◽  
Circular Dna ◽  
Transmission Electron ◽  
Electron Microscopic Technique

Gordon and Kleinschmidt have described a new preparative technique for visualizing DNA by electron microscopy. This procedure, which is a modification of Hall's “mica substrate technique”, consists of the following steps: (a) K+ ions on the cleavage surface of native mica are exchanged for Al3+ ions by ion exchange. (b) The mica, with Al3+ in the exchange sites on the surface, is placed in a dilute aqueous salt solution of DNA for several minutes; during this period DNA becomes adsorbed on the surface. (c) The mica with adsorbed DNA is removed from the DNA solution, rinsed, dried and visualized for transmission electron microscopy by Hall's platinum pre-shadow replica technique.In previous studies of circular DNA by this technique, most of the molecules seen were either broken to linears or extensively tangled; in general, it was not possible to obtain suitably large samples of open extended molecules for contour length measurements.

Existence of DNA in yeast microbodies

1978 ◽  
Vol 36 (2) ◽  
pp. 232-233
Author(s):  
Masako Osumi ◽  
Misuzu Nagano ◽  
Hiroko Kazama
Keyword(s):  
Catalase Activity ◽  
Buoyant Density ◽  
Model System ◽  
Contour Length ◽  
Native State ◽  
Normal Alkane ◽  
Remarkable Increase ◽  
Dna Molecule ◽  
Mitochondrial Dnas

We have found that microbodies appeared profusely together with a remarkable increase in catalase activity in normal alkane-grown cells of hydrocarbon-utilizing Candida yeasts, and that the microbodies multiplied by division in these cells. These features of Candida yeasts seem to provide a useful model system for studies on the biogenesis of the microbody. Subsequently, we have succeeded in isolation of Candida microbodies in an apparently native state, as judged biochemically and morphologically. The presence of DNA in the purified microbody fraction thus obtained was proved by the diphenylamine method. DNA molecule of about 15 urn in contour length was released from an isolated microbody. The physicochemical analyses of the microbody DNA revealed that its buoyant density differed from nuclear and mitochondrial DNAs. All these results lead us to the possibility that there is a novel type of DNA in microbodies.

Nucleic Acid Molecules Prepared by Monolayer Techniques

1972 ◽  
Vol 30 ◽  
pp. 178-179
Author(s):  
Dimitrij Lang
Keyword(s):  
Electron Microscopy ◽  
Standard Deviation ◽  
Nucleic Acid ◽  
Cytochrome C ◽  
Nucleic Acids ◽  
Contour Length ◽  
Sample Standard Deviation ◽  
Molecular Weights ◽  
Length Measurements ◽  
Protein Monolayer

The success of the protein monolayer technique for electron microscopy of individual DNA molecules is based on the prevention of aggregation and orientation of the molecules during drying on specimen grids. DNA adsorbs first to a surface-denatured, insoluble cytochrome c monolayer which is then transferred to grids, without major distortion, by touching. Fig. 1 shows three basic procedures which, modified or not, permit the study of various important properties of nucleic acids, either in concert with other methods or exclusively:1) Molecular weights relative to DNA standards as well as number distributions of molecular weights can be obtained from contour length measurements with a sample standard deviation between 1 and 4%.

Quantification of cell-surface expressed antigenic sites with 5-nm gold markers: Getting close to biologically relevant data

1989 ◽  
Vol 47 ◽  
pp. 1050-1051
Author(s):  
Etienne de Harven ◽  
Hilary Christensen ◽  
Richard Leung ◽  
Cameron Ackerley
Keyword(s):  
Cell Surface ◽  
Human Peripheral Blood ◽  
Contour Length ◽  
Thin Sections ◽  
Gold Particles ◽  
Biologically Relevant ◽  
Transmission Electron ◽  
Entire Cell ◽  
Electron Imaging ◽  
Cell Contour

The T-derived subset of human peripheral blood normal lymphocytes has been selected as a model system to study the usefulness of 5 nm gold markers for quantification of single epitopes expressed on cell surfaces. The chosen epitopes are parts of the CD3 and CD5 molecules and can be specifically identified by hybridoma produced monoclonal antibodies (MoAbs; LEU-4 and LEU-1; Becton-Dick- inson, Mountain view, CA) . An indirect immunolabeling procedure, with goat anti-murine IgG adsorbed on the surface of 5 nm colloidal gold particles (GAM-G5, Janssen Pharmaceutica, Beerse, Belgium) has been used. Backscattered Electron Imaging (BEI) in a field emission scanning electronmicroscope (SEM) and transmission electron microscopy of thin sections of lymphocytes labeled before plastic embedding, were both used to identify and quantitate gold labeled cell surface sites, Estimating that the thickness of “silver” sections is approximately 60 nm and counting the number of gold particles on the entire cell perimeter, we calculated that, for LEU-4, the number of markers per um2 of cell surface is in the 140-160 range (Fig.l). Cell contour length measurements indicated that the surface of one lymphocyte is approximately 130-160 um2 that of a smooth sphere of identical diameter, reflecting the role of microvilli in expanding the surface area. The total number of gold labeled sites on the surface of one lymphocyte averages, therefore between 20,000 and 24,000 per cell.

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