Viscoelastk Properties of Polymer Solutions in High-Viscosity Solvents and Limiting High-Frequency Behavior. I. Polystyrene and Poly(α-methylstyreste)

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. SynopsisWe study theoretically the formation of shear bands in time-dependent flows of polymeric and wormlike micellar surfactant fluids, focussing on the protocols of step shear stress, step shear strain (or in practice a rapid strain ramp), and shear startup, which are commonly studied experimentally. For each protocol we perform a linear stability analysis to provide a fluid-universal criterion for the onset of shear banding, following our recent letter [Moorcroft and Fielding, Phys. Rev. Lett. 110, 086001 (2013)]. In each case this criterion depends only on the shape of the experimentally measured rheological response function for that protocol, independent of the constitutive properties of the material in question (Therefore our criteria in fact concern all complex fluids and not just the polymeric ones of interest here.). An important prediction is that pronounced banding can arise transiently in each of these protocols, even in fluids for which the underlying constitutive curve of stress as a function of strain-rate is monotonic and a steadily flowing state is accordingly unbanded. For each protocol we provide numerical results in the rolie-poly and Giesekus models that support our predictions. We comment on the ability of the rolie-poly model to capture the observed experimental phenomenology and on the failure of the Giesekus model. V C 2014 The Society of Rheology.

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“…This protocol has been extensively studied experimentally in entangled polymeric fluids 26,27,46,[64][65][66][67]78,81,85 .…”

Section: B Strain Rampmentioning

confidence: 99%

Shear banding in time-dependent flows of polymers and wormlike micelles

Moorcroft¹,

Fielding²

2014

Journal of Rheology

122

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“…Such measurements have usually been made at somewhat higher concentrations (28) than the low-frequency measurements described above, and extrapolation to infinite dilution has been made only in the high-frequency region where the concentration dependence is relatively slight (31-34). The proportionality of G" -WT]s to w implies that the dynamic viscosity, Tl 1 :: G" /w, becomes independent of w at high frequencies and levels off at a value n'~ greater than T]s' corresponding to a finite high-frequency intrinsic dynamic viscosity In'] • The latter can be obtained as the slope of a plot of ln (n' /n ) against c (32). It is i~dependent of s molecular weight, and for polystyrene (33) it is also independent of branching (both star and comb shapes), However, for different polymers it depends considerably on the chemical structure (34,35).…”

Section: Rigid Elongated Macromoleculesmentioning

confidence: 99%

Viscoelastic properties of dilute polymer solutions

Ferry¹

1978

Pure and Applied Chemistry

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-The frequency dependences of the intrinsic storage and lass shear moduli can be predicted from molecular theories for flexible random coil polymers (beadspring models) and for rigid elongated macromolecules. Camparisan with various experimental data extrapolated to infinite dilution shows good agreement with both these extreme types. For semi-rigid helical macromolecules, and for highly charged polyelectrolytes, experimental data correspond to hybrid relaxation spectra which are attributed to rigid-body rotation tagether with certain internal motions --probably flexural modes for the helices, configurational rearrangements for the polyelectrolytes. At high frequencies or in high-viscosity solvents, additional energy dissipation mechanisms appear in random coil polymers, whose nature is still conjectural.

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“…Experimental studies of the frequency dependence of linear viscoelastic (VE) [1][2][3][4][5][6][7][8][9][10][11] and oscillatory flow birefringence (OFB) [12][13][14][15][16][17][18][19][20][21][22][23] properties of dilute and semidilute polymer solutions provide considerable insight into the dynamics of conformational change in macromolecules. In both experiments, one applies a force of variable frequency that produces a simple shearing flow of very small amplitude and measures the response of the sample.…”

Section: Introductionmentioning

confidence: 99%

Apparent relaxation‐time spectrum cutoff in dilute polymer solutions: An effect of solvent dynamics

Peterson

Echeverría

Hahn

et al. 2001

J Polym Sci B Polym Phys

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ABSTRACT:The apparent short time cutoff of the relaxation-time spectrum at surprisingly long times for polymers in solution is a well known but not yet understood observation. To elucidate its origins we revisit viscoelastic and oscillatory flow birefringence data for solutions and melts of two linear polymers (polystyrene and polyisoprene) and present new measurements of oscillatory flow birefringence of the latter. Previous measurements have suggested that the "flexibility" of both polymers in solution is smaller than in the melt on the basis of the breadth of the relaxation-time spectrum of the solution as compared with that of the melt. Our new measurements have explored a higher effective frequency range than was previously possible. This has allowed us to observe the effect of the rotational relaxation time of the solvent on the dynamics of the solution at high frequencies. To obtain the polymer global motion contribution, one now needs to subtract from the solution properties a frequencydependent complex solvating environment contribution. We show that the decrease in apparent "flexibility" for solutions arises from the presence of a solvent that exhibits a rotational relaxation time and thus simple viscoelastic behavior somewhat near the frequency window of the experiment. Although recent predictions of a model for a chain in a solvent with a single relaxation time are in qualitative agreement with our results, our data suggest that the solution results may reflect the influence of solvent on the development of the "entropic spring" forces at short times.

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Viscoelastk Properties of Polymer Solutions in High-Viscosity Solvents and Limiting High-Frequency Behavior. I. Polystyrene and Poly(α-methylstyreste)

Cited by 47 publications

References 15 publications

Shear banding in time-dependent flows of polymers and wormlike micelles

Shear banding in time-dependent flows of polymers and wormlike micelles

Viscoelastic properties of dilute polymer solutions

Apparent relaxation‐time spectrum cutoff in dilute polymer solutions: An effect of solvent dynamics

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