microemulsions: basic theory and structure...

University of Cologne

Microemulsions: Basic Theory

and

Structure Kinetics

Dr. Helge Klemmer Physical Chemistry, University of Cologne, D-50939 Köln,

Germany

MN-C-WP/c

Sommersemester 2014


Low surfactant content, low energy input: emulsions

(usually micrometer size, very instable)

Low surfactant content, high energy input: nanoemulsions

(usually nanometer size, slightly kinetically stable)

High surfactant content, just thermal energy: microemulsions

(lower nanometer size, thermodynamically stable)

Non-amphiphile systems: e.g. Pickering emulsions

2

It‘s the amphiphile content that matters


3

Microemulsions

hydrophililic —hydrophobic—amphiphilic

component

(A) — (B) — (C)

thermodynamically stable, macroscopically homogeneous

but nano-structured phases of at least 3 components

water glycerol

monomers

n-alkanes triglycerides, monomers

super-critical fluids

non-ionic & ionic

surfactants


4

Binary Water – Surfactant Systems / Surfactant types

non-ionic surfactants

ethylene glycol monoalkyl ether (CiEj)

alkylpolyglucoside (CiGj)

ionic surfactants

sodium bis(2-ethylhexyl) sulphosuccinate (AOT) anionic

dodecyl trimethylammonium bromide (DTAB) cationic


5

Binary side-systems


6

Water (A) – CiEj (B) Systems / upper miscibility gap

a

A C

2

cp

CA

C

mm

m

T

tie-line

critical point cp


7

Water (A) – C12Ej (B) / Variation of j


8

Water (A) – CiEj (B) / Micelle formation - cmc

c

1e-7 1e-6 1e-5 1e-4 1e-3 1e-2

/

mN

m-1

0

10

20

30

40

50

60

70

80

H2O - Tensid

cmc

TpdA

dE

,

Gibbs adsorptions isotherm:

Tpcd

d

RT ,ln

1

Surfactant head group area:

ANa

1

Surface tension:


9

Water – CiEj Systems / Liquid crystalline phases

micellar cubic (I1):

hexagonal (H1):

bicontinuous cubic (V1):

lamellar (La):

+ inverted liquid crystalline phases:

V2, H2, I2


10 0.001 0.01 0.1 1

T /

°C

0

10

20

30

40

50

60

70

80

90

2

1

spheres

cylinders

networks

Water – C12E6 / more self-assembly

wB

T /

°C

1

2

32_

T1 T1

T2

T2

T3

T3

H2O / C

iE

j

oil


11

Water – C12E5 System / dilute self-assembled phases

/ wt%

0.001 0.01 0.1 1 10 1000

20

40

60

80

100

C12E6

C12E5

C12E4

2

1

/ wt%

0.001 0.01 0.1 1 10 100

T /

°C

0

20

40

60

80

100

L1

L1'+L3

L3

La

L2

H1

cmc

L1'+L1''

L1'+L2

wB

T /

°C

1

2

32_

T1 T1

T2

T2

T3

T3

H2O / C

iE

j

oil

L2: reversed micelles

dilute lamellae

L3: isotropic bi-

layer sponge-

phase


12

Gibbs phase prism

p = constant


13

Sections through the phase prism

BA

B

mm

m

a

CBA

C

mmm

m


14

Isothermal sections - phase inversion


15


BA

B

mm

m

a

CBA

C

mmm

m


16

Isoplethal T()-section I

~

Measure of

Efficieny:

Phase inversion:

Monomeric

solubility:

T~

0

F = 0.50 = const.


17

Isoplethal T()-section II

F = 0.50 = const.

H2O - n-octane - CiEj

= 0.5

0.0 0.1 0.2 0.3 0.4 0.5

0

20

40

60

0

20

40

60

T / °C

0

20

40

60

0

20

40

60

80

C10E4

C8E3

C6E2

1

1

13

32

2

23

C12E5

T / °C

T / °C

T / °C

La3

La

La

2_

2_

2_

1

2_

V

H2O – n-octane – CiEj


18

Efficiency – Phase inversion temperature

F = 0.50 = const.

H2O – n-octane – CiEj


19

Phase behaviour – Interfacial tensions

Microemulsions, T. Sottmann and R. Strey in Fundamentals of Interface and Colloid Science,

Volume V, edited by J. Lyklema, Academic Press (2005)


20

Variation of oil/water-interfacial tension

T. Sottmann and R. Strey, J. Chem. Phys. 106, 8606 (1997)

T / °C

0 10 20 30 40 50 60 70

ab /

mN

m-1

10-4

10-3

10-2

10-1

100

H2O - n-C8H18 - CiEj

C12E5

C10E4

C8E3

C6E2

C4E1


21

Microstructure

Techniques:

direct: Transmission Electron Microscopy (TEM)

indirect: Scattering Techniques

• Small Angle Neutron Scattering (SANS)

• Small Angle X-Ray Scattering

• Dynamic Light Scattering

Diffusion NMR

Electric Conductivity


22

R. Strey, Colloid Polym. Sci., 272 (8), 1005 (1994).

F = 0.50 = const.

Microstructure


23

Microstructure – Length Scales

Small angle neutron scattering (SANS)

q / Å-1

10-3 10-2 10-1 100

I(q

) /

cm-1

10-1

100

101

102

103

D2O - n-C8D18 - C12E5

a=0.0707, wB=0.0561, T=18°C

S(q)

P(q)

I(q)

r = 61.2 Å

= 9.7 Å

t = 6.0 Å

Iincoh= 0.125 cm-1

o/w

q / Å-1

10-3 10-2 10-1 100

I(q

) /

cm-1

10-1

100

101

102

103

D2O - n-C8D18 - C12E5

b=0.1260, wA=0.0959, T=46°C

S(q)

P(q)

I(q)

r = 50.0 Å

= 12.0 Å

t = 6.0 Å

Iincoh= 0.16 cm-1

w/o

M. Gradzielski, D. Langevin, L. Magid, and R. Strey, J. Phys. Chem. 99, 13232 (1995)

bicontinuous

D2O - n-octane - C12E5

q / Å-1

10-3 10-2 10-1

I ( q

) /

cm-1

10-1

100

101

102

103

104

105

106

107

108

109

1010

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.9

M. Teubner and R. Strey, J. Chem. Phys. 87, 3195 (1987)

University of Cologne 24 Redrawn from:

Strey, R., Colloid Polym. Sci., 1994, 272 (8), 1005.

Gompper, G., Kroll, D. M., Phys. Rev. Lett., 1998, 81, 2284.

Non-ionic surfactant (C)

H2O (A) alkane (B)

CB

Cb

mm

m

BA

B

mm

m

a



The T(wA)-Cut

25

D2O/NaCl – cyclohexane-h12 – C10E5 e = 0.001, b=0.05, T=24.50°C

total

AA

m

mw

CB

Cb

mm

m

A

NaCl

m

me


The Mixing Pathway

26

D2O/NaCl – cyclohexane-h12 – C10E5 e = 0.001, b=0.05, T=24.50°C

total

AA

m

mw

CB

Cb

mm

m

A

NaCl

m

me

D2O/NaCl (A) cyclohexane (B)

1

2

C10E5 (C)

University of Cologne 27

High temperature stability:

DT ≤ 0.1 K for 273 K ≤ T ≤ 343 K

BioLogic stopped flow combined

with:

The Experimental Setup


D2O/NaCl – cyclohexane-h12 – C10E5

b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

Microemulsion Formation Kinetics



b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5




b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms




b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms

J. S. Pedersen, J Appl Crystallogr, 1994, 27, 595-608.

M. Kotlarchyk, S. H. Chen and J. S. Huang, Phys Rev A, 1983, 28, 508-511.

M. Gradzielski, D. Langevin, L. Magid and R. Strey, J Phys Chem-Us, 1995, 99, 13232-13238.

T. Foster, T. Sottmann, R. Schweins and R. Strey, J Chem Phys, 2008, 128.





b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms









b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms t = 134 ms








t = 539 ms

34


b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms








t = 539 ms

35


b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms








t = 891 ms

36


b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms








t = 1408 ms

37


b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms








t = 2163 ms

38


b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms








t = 3269 ms

39


b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms








t = 180000 ms

40


b = 0.05

e = 0.001 T = 24.50°C

wA = 0.11

D2O/NaCl

c-B6/C10E5

t = 22 ms








twater-uptake = (430±35) ms

t

t

eAt

Fdrop

Time-resolved Water Uptake


µE,0µE reAtr

t

t

42

twater-uptake = (430±35) ms

tradial growth = (260±99) ms

Time-resolved Radial Growth


The Influence of Amphiphilic Polymers

D2O/NaCl – cyclohexane-h12 – C10E5/PEB4.8-PEO4.8

e = 0.001, b=0.05

Bulk contrast

D2O/NaCl – cyclohexane-d12 – C10E5/PEB4.8-PEO4.8

e = 0.001, b=0.05

Film contrast

43



e = 0.001, b=0.05, d = 0.05 (bulk contrast)










twater-uptake = (313±48) ms tradial growth = (1600±167) ms



D2O/NaCl – cyclohexane-d/h12 – C10E5/PEB4.8-PEO4.8

e = 0.001, b=0.05, d = 0.05 (film contrast)










twater-uptake = (98±13) ms tradial growth = (6215±1436) ms



D2O/NaCl – cyclohexane-d/h12 – C10E5/PEB4.8-PEO4.8









52

Theoretical background

T. Sottmann and R. Strey, J. Chem. Phys. 106, 8606 (1997)

Thermodynamic stability:

Structure size approximation:

Specific internal interface:

Droplet radius approximation:

Approximate structure size:

²TkB

VSa

/

)1(

c

cic

v

aVS ,/

iC

Ac

iC

A

c

c la

vR

,,

33

minmax//2 q

microemulsions: basic theory and structure...

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