Phase separation in dilute polymer solutions at high‐rate extension

Субботин, А. А.; Semenov, A. N.

doi:10.1002/polb.24005

Cited by 25 publications

(73 citation statements)

References 26 publications

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“…We find that for the aforementioned three molecular weights, the estimates for Zimm time obtained by using monomeric friction values extracted from DoS rheometry measurements are of the same order of magnitude as those obtained using the formula

λ_{z} = \frac{1}{ζ (3 ν)} \frac{[η] η_{s} M_{w}}{R T}

. However, other factors like amplified concentration fluctuations, possible role of topological constraints, conformational anisotropy and the resulting influence on the overall drag coefficient and on the relaxation dynamics, are not captured by eq , and these warrant further investigation …”

Section: Resultsmentioning

confidence: 82%

Pinch‐off dynamics and extensional relaxation times of intrinsically semi‐dilute polymer solutions characterized by dripping‐onto‐substrate rheometry

Dinic

Biagioli

Sharma

2017

J Polym Sci B Polym Phys

169

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Stream‐wise velocity‐gradients associated with extensional flows arise in thinning liquid necks spontaneously formed during jetting, printing, coating, spraying, atomization, and microfluidic‐based drop formation. In this contribution, we employ Dripping‐onto‐Substrate (DoS) rheometry protocols to measure the extensional rheology response of intrinsically semi‐dilute polymer solutions by visualizing and analyzing capillary‐driven thinning of a columnar neck formed between a nozzle and a sessile drop. We show that extensional viscosity that quantifies the resistance to stream‐wise velocity gradients is orders of magnitude higher than the shear viscosity. Although shear flows only weakly perturb the chain dimensions, extensional flows can strongly stretch and orient the chains, thus influencing both intra‐ and inter‐chain interactions. We find that the extensional relaxation times for intrinsically semi‐dilute PEO solutions in a good solvent for five different molecular weights increase linearly with concentration, exhibiting a stronger concentration dependence than observed for dilute solutions, or anticipated by blob models, developed for relaxation of weakly perturbed chains in a good solvent. The observed distinction between the concentration‐dependent relaxation dynamics of intrinsically dilute and semi‐dilute solutions arises due the complex influence of stretching, conformational anisotropy, and polymer concentration on excluded volume and hydrodynamic interactions of flexible, highly extensible polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1692–1704

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λ_{z} = \frac{1}{ζ (3 ν)} \frac{[η] η_{s} M_{w}}{R T}

Section: Resultsmentioning

confidence: 82%

Pinch‐off dynamics and extensional relaxation times of intrinsically semi‐dilute polymer solutions characterized by dripping‐onto‐substrate rheometry

Dinic

Biagioli

Sharma

2017

J Polym Sci B Polym Phys

169

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“…The elastic force is defined by the elastic free energy per chain:

F_{el} ≃ \frac{T L}{2 l} \overset{F}{true} (s),

where l is the Kuhn segment length (

l = a_{s}^{2} / l_{1}

), and the function

\overset{F}{true} (s)

is parametrically defined by the following equations:

\overset{F}{true} = A \coth (A) - 1, s = \coth (A) - 1 / A

…”

Section: The Model and The Coil–stretch Transitionmentioning

confidence: 99%

“…The underlying rheological phenomena are complicated and are not understood well theoretically; hence, we chose to start their analysis with a simpler unentangled regime. Recently we considered the demixing instability induced by a sufficiently fast elongational flow in unentangled polymer solutions . The instability is associated with the extension‐induced coil to stretched coil transition.…”

Section: Introductionmentioning

confidence: 99%

“…The magnitude of this thermodynamic driving force is proportional to

ϕ N T

per polymer chain, where

ϕ

is the polymer volume fraction, so it dominates the SCC effect as long as

ϕ N T ≫ T

. It is predicted that uniaxial extensional flow can induce demixing in polymer solutions if the extension rate exceeds some critical value (

Wi > {Wi}_{c} \sim 1

). This effect differs from the capillary breakage of polymer jets due to Plateau–Rayleigh instability, which does not necessarily imply any demixing of the system.…”

Section: Introductionmentioning

confidence: 99%

“…The aim of this study is to describe theoretically how the phase separation process in an unentangled (dilute or semidilute) polymer solution proceeds upon its fast extension, and what sort of eventual polymer jet structure is expected . Note that the demixing mechanism considered here is akin to, but is different from the conformational deformation effect of shear flow leading to a shift of the critical point for polymer solutions …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Phase separation kinetics in unentangled polymer solutions under high‐rate extension

Semenov

Субботин

2017

J Polym Sci B Polym Phys

Self Cite

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Phase separation processes following high‐rate extension in unentangled polymer solutions are studied theoretically. The flow‐induced demixing is associated with the coil–stretch transition predicted in high‐molecular‐weight polymer solutions at high‐enough Weissenberg numbers. The developed mean‐field theory is valid in the dilute/semidilute solution regime, where the stretched coils overlap strongly. We elucidate and discuss the main kinetic stages of the polymer/solvent separation process including (i) growth of concentration fluctuations and formation of oriented protofibrils by anisotropic spinodal decomposition; (ii) development of well‐defined highly oriented and stiff fibrils forming an anisotropic network (cross‐linked fiber); (iii) microphase separation and lateral collapse of the network yielding dense oriented fiber. These novel predictions are in qualitative agreement with the experimental data. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 623–637

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Electrospinning and Mechanotropic Phenomena in Polymer Solutions

Kotomin

Malkin

Skvortsov

2020

Macromolecular Symposia

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The mechanism of electrospinning traditionally is related to fast evaporation of solvent from thin liquid jets of polymer solution observed in high-voltage electric fields. Another mechanism, called mechanotropic spinning, is more reasonable for polymer solutions in solvents having low vapor pressure and high boiling temperature, that is, dimethylacetamide (DMAc), DMF, dimethyl sulfoxide (DMSO). Under elongation, the solution undergoes phase separation as a result of high-speed stretching and the solvent reveals on the surface of the fiber without its complete evaporation. Microfibers obtained by mechanotropic spinning as well as by electrospinning of PAN solutions in DMSO and polyamidbenzamidazol in DMAc have stable droplets of the solvent on the fiber surface.

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Phase separation in dilute polymer solutions at high‐rate extension

Cited by 25 publications

References 26 publications

Pinch‐off dynamics and extensional relaxation times of intrinsically semi‐dilute polymer solutions characterized by dripping‐onto‐substrate rheometry

Pinch‐off dynamics and extensional relaxation times of intrinsically semi‐dilute polymer solutions characterized by dripping‐onto‐substrate rheometry

Phase separation kinetics in unentangled polymer solutions under high‐rate extension

Electrospinning and Mechanotropic Phenomena in Polymer Solutions

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