Relaxation of dilute polymer solutions following extensional flow

Doyle, Patrick S.; Shaqfeh, Eric S. G.; McKinley, Gareth H.; Spiegelberg, Stephen H.

doi:10.1016/s0377-0257(97)00113-4

Cited by 137 publications

(81 citation statements)

References 39 publications

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“…85 In principle, this allows us to manipulate the suspension structure down to the single particle scale in a sheared sample. Our three-axis piezoelectric stage additionally allows us to investigate compressional or extensional flows in complex fluids, 86,87 simply by taking advantage of the y-positioning capabilities of the piezo to move the plates perpendicular to the sample boundaries. Moreover, by mis-aligning the top and bottom plates, we can use our shear apparatus to investigate shear or compressional lubrication flows in complex fluids.…”

Section: Other Applicationsmentioning

confidence: 99%

A multi-axis confocal rheoscope for studying shear flow of structured fluids

Lin

McCoy

Cheng

et al. 2014

Review of Scientific Instruments

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We present a new design for a confocal rheoscope that enables uniform uniaxial or biaxial shear. The design consists of two precisely positioned parallel plates with a gap that can be adjusted down to 2 ±0.1 μm, allowing for the exploration of confinement effects. By using our shear cell in conjunction with a biaxial force measurement device and a high-speed confocal microscope, we are able to measure the real-time biaxial stress while simultaneously imaging the material three-dimensional structure. We illustrate the importance of the instrument capabilities by discussing the applications of this instrument in current and future research topics in colloidal suspensions. © 2014 AIP Publishing LLC.[http://dx

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Section: Other Applicationsmentioning

confidence: 99%

A multi-axis confocal rheoscope for studying shear flow of structured fluids

Lin

McCoy

Cheng

et al. 2014

Review of Scientific Instruments

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“…Therefore, at any instant, the above terms are taken to be independent of the distribution Q but dependent on the ensemble average of Q 2 . Recent studies 46,47 have shown that preaveraging can be inaccurate in strong flows; however, for steady-state flows, preaveraging seems to be an acceptable approximation. 44,48 Before integrating the evolution equations over configuration space, we introduce the dimensionless conformation tensors A for the bridging chains and B for the temporary dangling chains, which are computed by averaging the approximate dyadic product QQ over the respective conformation distribution spaces to give where l c ) Nb 2 /3 is the characteristic length for scaling such that tr A eq ) tr B eq ) 3.…”

Section: Constitutive Equationmentioning

confidence: 99%

Rheology and Dynamics of Associative Polymers in Shear and Extension: Theory and Experiments

2006

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We investigate the steady and transient shear and extensional rheological properties of a series of model hydrophobically modified ethoxylate-urethane (HEUR) polymers with varying degrees of hydrophobicity. A new nonlinear two-species network model for these telechelic polymers is described which incorporates appropriate molecular mechanisms for the creation and destruction of elastically active chains. Like other recent models we incorporate the contributions of both the bridging chains (those between micelles) and the dangling chains to the final stress tensor. This gives rise to two distinct relaxation time scales: a short Rouse time for the relaxing chains and a longer network time scale that depends on the aggregation number and strength of the micellar junctions. The evolution equations for the fraction of elastically active chains and for the conformation tensors of each species are solved to obtain the total stress arising from imposed deformations. The model contains a single adjustable nonlinear parameter and incorporates the nonlinear chain extension, the shear-induced enhancement of associations, and the stretch-induced dissociation of hydrophobic chains. In contrast to earlier closed-form models, we are able to obtain quantitative agreement between experimental measurements and the model predictions for three different series of telechelic polymers over a range of concentrations. The scaling of both the zero shear viscosity and the effective network relaxation time shows good agreement with those measured in experiments. The model also quantitatively captures both the shear thickening and subsequent shear thinning observed in the rheology at high deformation rates and predicts transient extensional stress growth curves in close agreement with those measured using a filament stretching rheometer.

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“…15 Furthermore, even if the initial tension distribution does relax during the unhooking process, bead-rod simulations show that because of nonlinear elasticity, very large changes in tension can result from very small shifts in a stretched configuration. 39 Therefore, the first-order model for an unhooking DNA is to consider an unhooking chain of constant length; we will consider both complete extension (L) and moderate extension (L ). We will term a model with constant extension the "J model" since it likely best describes J collisions.…”

Section: Unhooking Time Modelsmentioning

confidence: 99%

Collision of a DNA Polymer with a Small Obstacle

2006

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Using single molecule fluorescence microscopy, we study the dynamics of an electric-field-driven DNA molecule colliding with a single stationary post. The radius of the obstacle is small compared to the contour length of the molecules. Molecules that achieve hooked configurations which span the obstacle were chosen for study. Four different types of hooked configurations were found: symmetric hairpins with constant extension during unhooking, asymmetric hairpins with constant extension during unhooking, asymmetric hairpins with increasing extension during unhooking, and rare multiply looped entangled configurations. The important physics describing the unhooking dynamics for each classification differ and models are proposed to predict unhooking times. Surprisingly, we find that most collisions do not follow classic rope-on-pulley motion but instead form hairpins with increasing total extension during the unhooking process (called X collisions). Last, we show that unraveling to form a hairpin and center-of-mass motion during unhooking affect the overall center of mass holdup time during a collision process.

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Relaxation of dilute polymer solutions following extensional flow

Cited by 137 publications

References 39 publications

A multi-axis confocal rheoscope for studying shear flow of structured fluids

A multi-axis confocal rheoscope for studying shear flow of structured fluids

Rheology and Dynamics of Associative Polymers in Shear and Extension: Theory and Experiments

Collision of a DNA Polymer with a Small Obstacle

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