Interfacial and bulk rheological properties of a thermoresponsive fatty acid assembly

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Interfacial and bulk rheological properties of a thermoresponsive fatty acid assembly

Anne-Laure Fameau, Arnaud Saint-Jalmes

To cite this version:

Anne-Laure Fameau, Arnaud Saint-Jalmes. Interfacial and bulk rheological properties of a thermore- sponsive fatty acid assembly. 9. European conference on foams, Emulsions and applications, Jul 2012, Lisbonne, Portugal. 1 p., 2012. �hal-02807224�

Interfacial and bulk rheological properties of a thermoresponsive fatty acid assembly

Anne-Laure Fameau ¹ and Arnaud Saint-Jalmes ²

1 INRA, Biopolymères Interactions Assemblages, rue de la Géraudière, 44316 Nantes, France.

2 Institut de Physique de Rennes, CNRS-Université Rennes 1, 35042 Rennes, France.

Bulk studies: Rheological properties of tubes in bulk?

- +

12-hydroxystearic acid ethanolamine

20 C

^{47 C}

^{50 C}

^{60 C}

^{70 C}

10µm

Evolution of the tube diameter as a function of the temperature

Thermoresponsive

supramolecular assembly:

transition between tubes and micelles

Conclusion

Rheological properties of tubes in bulk and at the interface are easily temperature tunable & Link between the tubes structure as a function of the temperature with their rheological properties

Link between microscopic scale (tubes structure) and macroscopic scale (rheological properties)

Neutron Reflectivity study

Fameau A.L. et al., J. Colloid Interface Science. 2010, 241, 38.

Fameau A.L. et al., J. Phys. Chem B. 2011, 115, 9033.

Fameau A.L. et al., J. Colloid Interface Science, 2011, 362, 397.

Fameau A.L. et al., Angewandte Chemie International Edition, 2011, 50, 8264.

References

Fatty acids are surfactants of particular interest since they can be extracted from agricultural resources. However, long-chain fatty acids are generally insoluble in water at room temperature. Here, we dispersed the 12-hydroxy stearic acid using ethanolamine as counter-ion. One obtains self-assembled multilayer tubes. Those tubes have a temperature tunable diameter and melt into micelles at high temperature. These tubes can adsorb at the air/water interface and the structure is thermoresponsive at the interface. The aim of this work is to determine both the rheological properties of tubes in bulk and at the air/water interface with temperature in order to establish the links between the fatty acids supramolecular arrangements (in bulk and at interface) and the rheological properties, as a function of the temperature.

Background & Objectives

Interfacial studies: Rheological properties of tubes at the air/water interface?

air

≈300 Å

air

D

2

O 21 Å

D

2

O

I [ a. u.]

10 1 0.1 0.01

0.001 0.0001 100 1000 10000 100000

0.01 0.1

q [Å

^-1

]

24°C 38°C 48°C 61°C

29°C 42°C 52°C

33°C 45°C 55°C

C2

I [ a. u.]

10 1 0.1 0.01

0.001 0.0001 100 1000 10000 100000

I [ a. u.]

10 1 0.1 0.01

0.001 0.0001 100 1000 10000 100000

I [ a. u.]

10 1 0.1 0.01

0.001 0.0001 100 1000 10000 100000

0.01 0.1

q [Å

^-1

]

0.01 0.1

q [Å

^-1

]

24°C 38°C 48°C 61°C

29°C 42°C 52°C

33°C 45°C 55°C 24°C

38°C 48°C 61°C

29°C 42°C 52°C

33°C 45°C 55°C

C2

TEM

SANS

bilayer

Self-assembled multilamellar tubes

z

fatty acids

(z)

0 0.02 0.04 0.06 0.08 0.8 1.0

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 10^-8

10^-7 10^-6 10^-5 10^-4 10^-3 10^-2

70°C 60°C 50°C

40°C

20°C

RQ

4

Q (Å

^-1

)

2π/∆Q

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 10^-10

10^-9 10^-8

Experimental data Model of tubes

RQ

4

Q (Å

^-1

)

0.01 0.1

10

^-5

10

^-3

10

^-1

10

¹

10

³

10

⁵

10

⁷

10

⁹

61°C 55°C 52°C 48°C 46°C 42°C 38°C 34°C 29°C 24°C

Q ( Å

^-1

)

I [a. u.]

20 30 40 50 60 70

240 280 320 360 400

Int erl aye r spaci ng ( Å )

Temperature(°C)

Interlayer spacing (=2Π/Q)

SANS

Interlayer spacing (=2Π/Q)

Interlayer spacing is tuned by the

temperature.

Tubes structure is thermoresponsive at the interface!

Rheological study

Tensiometry measurements:

pendant drop method

Adsorption of tubes at the interface below a fatty acid monolayer!

Small Angle Neutron Scattering study Rheological study

Viscosity measurements with temperature:

Couette experiments

(Steady-shear measurements & gap of 1,1315 mm )

20 30 40 50 60 70

1 10 100 1000 10000

0.005 s

^-1

0.15 s

^-1

0.02 s

^-1

1 s

^-1

0.056 s

^-1

7.2 s

^-1

Visc osit y (m Pa/s )

Temperature (°C)

Oscillation amplitude of 5%

&

Frequency of 0,01Hz At equilibrium after 1000 s

20 30 40 50 60 70

22 23 24 25 26 27 28 29 30

Surface t en sio n (mN/m)

Temperature (°C)

20 30 40 50 60 70

10 100

Ela stic dil atio na l mod ul us (mN /m)

Temperature (°C)

The viscosity of the tubes in bulk depends on the temperature and it is linked to the tubes

structure (tubes diameter)!

The dilational interfacial viscoelastic moduli depend on the temperature and it is linked to

the structure at the interface!

Solutions of tubes are very shear-

thinning at all temperatures!