Dynamics of polymers in elongational flow studied by the neutron spin-echo technique

Rheinstädter, Maikel C.; Sattler, Rainer; Häußler, W.; Wagner, Christian

doi:10.1016/j.physb.2010.05.067

Cited by 2 publications

(1 citation statement)

References 13 publications

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“…The extensional relaxation time data for aqueous semi‐dilute PEO solutions with molecular weights of

6 \times 10^{5}, 1 \times 10^{6}, and 2 \times 10^{6} g / mol

provide a self‐consistent estimate for the

λ_{E} / λ_{o} N^{2}

), and the three datasets yield the monomer relaxation time

λ_{o}

values of 1.18, 1.24, and 1.38 ns, respectively. The values are marginally higher than the value estimated using

λ_{o} \approx η_{s} b^{3} / k T = 0.29 ns

, and the extension‐rate dependent values obtained from neutron spin echo measurements (segmental relaxation time of 117 ps was reported for an extension rate of 4 s −1 ). Thus, it is possible to make an estimate for Zimm relaxation time using

λ_{Z} \approx λ_{o} N^{3 υ}

as well as Rouse relaxation time using

λ_{o}

values extracted from DoS rheometry data.…”

Section: Resultscontrasting

confidence: 53%

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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“…The extensional relaxation time data for aqueous semi‐dilute PEO solutions with molecular weights of