Fluid-fluid pinch-off in presence of polymeric surface agents

Matthieu ROCHÉ (1), Hamid KELLAYCPMOH, Universite Bordeaux 1, France

(1) Now at Complex fluids groupMAE – Princeton University

APS DFD Meeting November, 22 2009

Minneapolis

Motivation

What happens if polymers are added to the outer fluid?

Polymeric fluids in airA viscous fluid in another

viscous fluid

)()(min ttth c )(min )( ttceth

[1] J. R. Lister and H. A. Stone, Phys. Fluids 10, 2758-2764 (1998).[2] I. Cohen, M. P. Brenner, J. Eggers, and S. R. Nagel, Phys. Rev. Lett. 83, 1147 (1999).[3] Y. Amarouchene, D. Bonn, J. Meunier, and H. Kellay, Phys. Rev. Lett. 86, 3558-3561 (2001).

[1,2] [3]

Polymers inside

Main observationsWith polymers lying at the interface between the

fluids, we observe that:Polymers in the outer phase modify the shape of

the neckPolymers in the outer phase modify the thinning

dynamicsStructures analogous to those observed with bulk

polymeric fluids (polymers inside the fluid led to break-up) arise during the thinning

We can obtain a good measurement of the surface viscosity induced by the presence of polymers

Set-up

Black: continuous outer phase (aqueous solutions of surface agents)White: to-be-dispersed inner phase (5CB liquid crystal)

Polymers in the outer phase only

Polymers in the outer phase modify the shape of the neck

= tc-t, time away from singularitytc: pinch-off time

[SDS] = 0.1 CMCNo PVA

[SDS] = 0.1 CMC[PVA] = 1 wt%Average Mw = 105 Da

Similarities between our experiments and the pinch-off of bulk polymeric fluids

a: M. S. N. Oliveira and G. H. McKinley, Phys. Fluids 17, 71704 (2005). Polymers inside the neck

b: R. Sattler, C. Wagner, and J. Eggers, Phys. Rev. Lett. 100, 3-6 (2008). Polymers inside the neck

c: our experiment. Polymers outside the neck

= tc-t, time away from singularitytc: pinch-off time

Qout=2 mL/h

sd = 3.89 ms

Polymers in the outer phase modify the thinning dynamics

hmin

Comparison between the thinning slowdown for bulk polymeric fluids and the slow-down we

observed

Y. Amarouchene, D. Bonn, J. Meunier, and H. Kellay, Phys. Rev. Lett. 86, 3558-3561 (2001).

Exponential tendency

The slow down is well fitted by an exponential function

= tc-t, time away from singularitytc: pinch-off time

[SDS] = 0.1 CMC[PVA] = 1 wt%

Qout=2 mL/h

sd = 3.89 ms

Observations for a silicone oil in a PVA outer solution : purely viscous effect

~1140 s-1

Effect not related to the properties of the liquid crystal

Surface viscosity induced by polymers lying on the interface

s

s on the order of a few 10-6 to a few 10-5 kg/s

Good order of magnitude compared to values

reported in the literature

Deflate Inflate

5CB in a 1 wt% PVA solution

Conclusion

Surface effects induced by polymers in the outer phase of a liquid-liquid system led to break-up

Growing structures analogous to those observed with bulk polymeric fluids, where polymers are inside the liquid led to break-up

Thinning dynamics for the neck similar to those observed with bulk polymeric fluids

Good agreement with reported values for surface viscosity of polymers