Structure and rheology of a shear-thickening wormlike ... · London, 4.9.007 Structure and rheology of a shear-thickening wormlike micellar system 1-4 Simultaneous formation of vorticity

London, 4.9.007

Structure and rheology of a shear-thickeningwormlike micellar system 1-4

Simultaneous formation of vorticity and velocitybands studied by birefringence measurements 1, 5, 6

1 Vishweshwara Herle, Peter Fischer2 Joachim Kohlbrecher

3 Cesare Olivero4 Sebastien Manneville5 Christophe Baravian

6 Francois Caton

1 Institute of Food Science, ETH Zurich, 8092 Zurich, Switzerland2 Paul Scherrer Institute, 5232 Villigen, Switzerland

3 Department of Chemistry, University of Calabria, 87036 Consenza, Italy4 Laboratoire de Physique, ENS Lyon, 69364 Lyon, France

5 LEMTA, CNRS - UMR, Nancy, France6 Laboratoire de Rheologie, Universite Grenoble, 38041 Grenoble, France

2/45 London, 4.9.007

A boring afternoon in the lab

3/45 London, 4.9.007

Micellar system under study

System: 40 mMol/L Cetylpyridinium chloride - Sodium salycilate

Shear Thickening

c 13 Pa

Newtonian

Shear thinning

Shear thickening

Formation of alternatingvorticity bands

Herle, V., Fischer, P., and Windhab, E. J. Langmuir 2005, 21, 9051

4/45 London, 4.9.007

Newtonian and shear thinning regime

Newtonian RegimeTransparent

Shear thinning regimeSlightly turbid

Optical appearance Stationary Cup

Rotating cylinderSample

5/45 London, 4.9.007

Shear thickening regime ( > c)

Shear Thickening

c 13 Pa

•Formation vorticity bands•Bands alternate in position•Shear rate and oscillates

Rheology, flow visualization and SALS -> Stress induced bands

I II III

Turbid

Transparent

1 second

6/45 London, 4.9.007

Rheology - transient shear flow

< c > c

No shear rate oscillations Shear rate oscillatesSample never equilibrates!

7/45 London, 4.9.007

Methods used & questions asked

Triggerd Rheo-Small Angle NeutronScattering (Rheo-SANS)

Newtonian clear =shear thickening clear?

Shear thinning turbid =shear thickening turbid?

Rheology & Flow visualization

Optical appearance (flip-flop) of bandscorrelated to rheological oscillations?

Influence of geometry?

8/45 London, 4.9.007

Methods used & questions asked

Direct birefringence measurements

Is there really a radial band withinthe vorticity band (sub-banding)

Fast camera, ultrasound VelocityProfiling (UVP), and Rheo-NMR

Wahst is the individual rheology ofthe clear and turbid bands?

9/45 London, 4.9.007

Vorticity bands & Rheology and SALS

Are the oscillations in viscosity andshear rate the same as in the

optical appearance of the bands?

Establish via optical rheometry and SALS the(obvious) link between ring formation and

oscillation of the free parameter

10/45 London, 4.9.007

Rheo-SSmall AAngle LLight SScattering Optical Imaging set up

|q|=0.25 - 1.0 μm-1

Both set-ups are designed for the Stress controlled rheometer (DSR)

Instrumentation (optical rheology)

11/45 London, 4.9.007

Power Spectrum

Oscillating shear rate signal from flow curvesand

Oscillating intensity signals from the shear bands

Fast Fourier Transform

Pmax

4 mm

Position I Position II

Analysis of the oscillating signal - FFT

12/45 London, 4.9.007

Flow visualization & Rheology

Oscillating shear bandsin parallel plate device

Rheological signal

Oscillations are indeed due to the flip-flop of the bands

Optical andmechanical signals

superimpose!

FFT


13/45 London, 4.9.007

Amplitude of rate oscillationincreases with stress @ constant gap(except for 0.10 mm)

Decrease in gap suppresses the rate oscillationsFor a gap of 0.10 mm-> NO0.10 mm is an exception!

Certain length scale is requiredfor band formation

Effect of gap size - Amplitude

14/45 London, 4.9.007


Structural buildup is determined by the rheometer gapHerle, V., Fischer, P., and Windhab, E. J. Langmuir 2005, 21, 9051

15/45 London, 4.9.007



Shear induced structures <---> Length scales

Lowering the gap•Shear thinning instead of thickening•Intensity of turbid bands decreases•More number of less intense bands•Oscillations of the are dampened

.

16/45 London, 4.9.007

Vorticity bands & SANS

What are the sstructures inthese bands?

How to access the structuralinformation in each band?

By triggering the SANS detector and selectivelycollecting the scattering for each band

17/45 London, 4.9.007

SANS - Set up

Neutron source: PSI SANS-I = 8 A

Detector dist. = 2, 6, and 18 mq range = 0.003 - 0.15 A-1°

°

NeutronbeamTo

detector

Suprasil GlassOuter cylinder dia = 32 mmInner cylinder dia = 30 mmGap = 1 mm

18/45 London, 4.9.007

Newtonian and Shear thinning regime

x = Flow directiony = Vel. gradient directionz = Vorticity direction

1. No significant anisotropyis observed

2. Partial alignment ofmicelles

Herle, V., Fischer, P., et al.: Phys. Rev. Lett., in press.

19/45 London, 4.9.007

SANS-Trigger Set-up

• Set a threshold value• Trigger the SANS detector• Collect the data

Laser

LaserDetector

Neutronbeam

To detector

20/45 London, 4.9.007

Triggered SANS measurements

1. Triggering the detector helps toseparate the scatteringinformation

2. Transparent state in this regimeis structurally different from theone in the Newtonian or shearthinning regime

3. Both transparent and turbidbands are highly anisotropic

4. Turbid state is more anisotropicthan transparent one


21/45 London, 4.9.007

SANS Analysis for flip-flop bands

II

I vs qq plot

Hayter model for sheared (solid) cylindersDia of micelles 40 angstromApprox. length of micelles 1200 angstrom Hayter, J.B. and Penfold, J.: J. Phys. Chem 88 (1984) 4589

22/45 London, 4.9.007

SANS Analysis for flip-flop bandsAnisotropy

*

Turbid band correspond to a more anisotrope state* Croce et. al. 2005, Langmuir

Schubert et. al. 2004, Langmuir

I(Q)

I(Q)||

23/45 London, 4.9.007

High speed camera

What are the vviscosity in the individual bands (Part I)?

How to access the rheology of each band?

Motion of rotation tool captured byhigh speed camera images

24/45 London, 4.9.007

Alternating Vorticity bands

•It is difficult to capture thedynamics of the process

•Does the oscillation in the toolreally corresponds to the bands?

•If yes, then, when the toolslows down and when itaccelerates?

•Finally, what are the structuresin these bands?

Problems and Questions

25/45 London, 4.9.007

Vorticity bands- AnalysisAnalysis of the bands and the position of the tool using LabView program

26/45 London, 4.9.007

Vorticity bands- Analysis

• As the turbid band appears velocity approaches zero• Implying turbid bands may be of higher viscosity!

Lower intensity -> transparent bandHigher intensity -> turbid band

I II III

Turbid

Transparent

1 second


27/45 London, 4.9.007

Vorticity bands & UVP

What are the vviscosity in theindividual bands (Part II)?

How to access the rheology ofeach band?

Is the turbid band more viscousthan the clear one?

By time-resolved Ultrasound Doppler Velocimetrycollecting the shear rate for each band

28/45 London, 4.9.007

UVP-Experimental Set-up

Manneville S: Eur. Phys.J.-Appl.Phys 28 (2004) 361

Newtonian With wall-slip Shear banding

v

0 e 0 e 0 e

v0

29/45 London, 4.9.007

UVP @ Newtonian and Shear thinning regime

•No radial banding in stress plateau regime as in conventional systems

•Flow is homogeneous

30/45 London, 4.9.007

UVP @ Shear thickening regime ( > c)

• Radial Banding is present• Flow is inhomogeneous• At higher stresses flow becomes chaotic!• Local velocity fluctuates as a function of time

31/45 London, 4.9.007

Local shear rates and time evolution ( > c)

Local shear rates in each band canbe calculated

This will give an idea about localshear rates

Position of the interface ( ) wasmonitored

1

.

2

.

32/45 London, 4.9.007

Local shear rates as a function of time ( > c)

In the Stress-plateau regime

1 and 2 are anticorrelated

2 and are correlated

33/45 London, 4.9.007

Local shear rates as a function of time @ 17 Pa

We do not see the vorticity bands (all turbid due to seeding):

• The behavior of local shear rates seems chaotic!• Is the flip-flop of the macroscopic motion hidden?

34/45 London, 4.9.007

Possible coexistence of radial and vorticity bands?

Vorticity banding

Newtonian flowShear-thinning flow

Radial shear banding

Coupled radial andvorticity bandingplus pretty muchnoise of rheo-chaos

35/45 London, 4.9.007

Vorticity bands & Direct birefringence

Do the sub-bands flip-flop?

How to access the structuralinformation in each band?

By direct birefringence measurement of eachband in the “chaotic regime”

36/45 London, 4.9.007

Direct birefringence - Set-up

Decruppe J.P. et al.: PRE 71 (2005) 011503

Laser close to outer cylinder

Laser close to innerrotating cylinder

37/45 London, 4.9.007

Radial sub-band found in vorticity bands

Outer cylinder:Inner cylinder (rotating):

Clear bandTurbid band Clear bandTurbid band

38/45 London, 4.9.007

Radial sub-band found in vorticity bands

Inner cylinder (rotating):

39/45 London, 4.9.007

Summary (1)

Vorticity bands correlate with the oscillation of the free rheological parameterGap effect suggest different lengthscale are relevant for rheological response

Optical andmechanical

signalssuperimpose!

F

F

T

40/45 London, 4.9.007

Summary (2)

Shear Thinning

Shear Thickening and vorticity bands

Isotropic at rest Partial Alignment

< c

Isotropic at rest Strong alignment(anisotropic)

Transparent (A) Turbid (B)

Rheo-SANS suggest the highest aligned band to be high viscous

41/45 London, 4.9.007

Summary (3)

As the turbid bandappears, velocityapproaches to Zero

Fast camera experiments show that the creating of turbid bandleads to oscillation in viscosity. Due to a phase difference of /2the system never reaches a steady state.

Turbid state is more anisotropic than transparent one

*

42/45 London, 4.9.007

Summary (4)

Local velocity measurements (Rheo-UVP) and Direct Birefringencemeasurements show the existence of coupled radial and vorticity banding

43/45 London, 4.9.007

Summary (5)

Is it a Russian Doll …

44/45 London, 4.9.007

… or scrap metal to be sold to China?

45/45 London, 4.9.007

Richard Nixon(quoted by Thomas Pynchon in “Gravities Rainbow”,

performed by Ernest in Sherman’s Lagoon)

Documents

Structure and rheology of a shear-thickening wormlike ... · London, 4.9.007 Structure and rheology of a shear-thickening wormlike micellar system 1-4 Simultaneous formation of vorticity