1. Fluid-fluid pinch-off in presence of polymeric surface agents
Matthieu ROCHÉ (1), Hamid KELLAY
CPMOH, Universite Bordeaux 1, France
(1) Now at Complex fluids group
MAE – Princeton University
APS DFD Meeting
November,
Minneapolis

2. What happens if polymers are added to the outer fluid?
Motivation
Polymers inside
[1,2]
[3]
A viscous fluid in another viscous fluid
Polymeric fluids in air
What happens if polymers are added to the outer fluid?
[1] J. R. Lister and H. A. Stone, Phys. Fluids 10, (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, (2001).

3. Main observations
With polymers lying at the interface between the fluids, we observe that:
Polymers in the outer phase modify the shape of the neck
Polymers in the outer phase modify the thinning dynamics
Structures 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

4. Polymers in the outer phase only
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

5. Polymers in the outer phase modify the shape of the neck
[SDS] = 0.1 CMC
No PVA
[SDS] = 0.1 CMC
[PVA] = 1 wt%
Average Mw = 105 Da
t = tc-t, time away from singularity
tc: pinch-off time

6. Similarities between our experiments and the pinch-off of bulk polymeric fluids
a: M. S. N. Oliveira and G. H. McKinley, Phys. Fluids 17, (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

7. Polymers in the outer phase modify the thinning dynamics
hmin
tsd = 3.89 ms
Qout=2 mL/h
t = tc-t, time away from singularity
tc: pinch-off time

8. Comparison between the thinning slowdown for bulk polymeric fluids and the slow-down we observed
Exponential tendency
Y. Amarouchene, D. Bonn, J. Meunier, and H. Kellay, Phys. Rev. Lett. 86, (2001).

9. The slow down is well fitted by an exponential function
tsd = 3.89 ms
[SDS] = 0.1 CMC
[PVA] = 1 wt%
Qout=2 mL/h
t = tc-t, time away from singularity
tc: pinch-off time

10. Effect not related to the properties of the liquid crystal
Observations for a silicone oil in a PVA outer solution : purely viscous effect
e ~1140 s-1
Effect not related to the properties of the liquid crystal

11. Surface viscosity induced by polymers lying on the interface
hs 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
5CB in a 1 wt% PVA solution
Deflate
Inflate

12. 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