Temporary Liquid Crystals in Microemulsion Systems - American

Chapter 6

Downloaded by NORTH CAROLINA STATE UNIV on May 3, 2015 | http://pubs.acs.org Publication Date: July 20, 1988 | doi: 10.1021/bk-1988-0373.ch006

Temporary Liquid Crystals in Microemulsion Systems 1

1

2

Stig E. Friberg , Zhuning Ma , and Parthasakha Neogi 1

2

Chemistry Department, Clarkson University, Potsdam, NY 13676 Chemical Engineering Department, University of Missouri-Rolla, Rolla, MO 65401 The transport processes between and inW/Omicroemulsions in contact with water were determined by direct analysis at different times of the concentrations of the components at different distances from the interface between the microemulsion and the water. The results demonstrated pronounced variation of the transport rate in different parts of the microemulsions when in contact with water. This variation caused an interface to appear within the o i l phase and also gave rise to temporary liquid crystals at high cosurfactant/surfactant content. The presence of high concentrations of salt changed the microemulsion region considerably, but had only limited effect on the transport properties. The main effect was that the duration of the liquid crystal presence was shortened and that an isotropic liquid middle phase was formed.

Mass transfer in surfactant systems is important in many areas. One such field that is particularly important is the surfactant flooding of oil fields (1-4), which is an attractive candidate for tertiary oil recovery. Consequently diffusional processes of aggregates such as micelles and microemulsions (5-9) have been studied extensively. In particular, contacting studies where two phases of varied constituents (surfactant, cosurfactant, oil, water, electrolyte) are in contact and results interpreted on the basis of mass transfer and phase diagrams have become the standard method for studying transport in such systems (10-18). Previously (11-12), we had contacted water and water in oil (W/0) microemulsion and found that transient lamellar liquid crystals (11) were formed even though these were not located in the pseudoternary phase diagram. The interesting feature was that these phases could be precipitated either in the oil phase or in the water phase, although the controlling factors could not be established. Because of its considerable significance in oil recovery (4) the mechanism of 0097-6156/88/0373-0108$08.00/0 « 1988 American Chemical Society In Surfactant-Based Mobility Control; Smith, D.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

6. FRIBERG ET AL.

Temporary Liquid Crystals in Microemulsions

109


the p r e c i p i t a t i o n of l i q u i d crystals i s under detailed investigation. The two possible reasons which govern the formation and location of l i q u i d c r y s t a l s are those of chemical potentials and d i f f u s i o n rates. It i s evident that the phenomenon i s similar to the s a l t i n g out process, however i t i s the competative d i f f u s i o n a l rates that govern the l o c a l concentrations and take the compositions outside the one phase areas. A lamellar l i q u i d c r y s t a l l i n e phase may then form. We found a c l a r i f i c a t i o n of the r e l a t i o n between d i f f u s i o n rates and the occurrence of temporary l i q u i d crystals to be of pronounced importance. With t h i s study we present results showing the concentration changes with time, which give r i s e to temporary l i q u i d c r y s t a l s .

Experimental Materials. The surfactant sodium dodecyl sulfate (SDS) from BDH Chemical Ltd., Poole, England, was twice r e c r y s t a l l i z e d from absolute ethanol. The cosurfactant, pentanol, the methanol, the s a l t , sodium chloride and the Karl Fisher reagent, which was used for water determination, were a l l from Fisher S c i e n t i f i c Company and c e r t i f i e d . The hydrocarbon, t-butylbenzene, with purity of 99% was from A l d r i c h Chemical Company, Inc. A l l of those were used without further p u r i f i c a t i o n . Twice d i s t i l l e d water was used. W/0 Microemulsion Regions. These were determined i n the following systems: 1. Sodium dodecyl s u l f a t e , pentanol and water; ( F i g . 1A). 2. Sodium dodecyl sulfate, pentanol and aqueous solution of sodium chloride with concentration of 0.5 M (Fig. IB) and 1 M (Fig. 1C). 3. Sodium dodecyl sulfate, water and pentanol/hydrocarbon (t-butylbenzene) (1:1 by weight) (Fig. ID). The W/0 microemulsion regions were found by t i t r a t i o n with water. Diffusion of Components. The d i f f u s i o n process was investigated i n the following manner: W/0 microemulsions with a minimum water content were c a r e f u l l y layered on top of water i n amounts to give a f i n a l composition of a W/0 microemulsion with a maxiumum water content. The layered samples were thermostated at 30°C and the variations i n layer height and interface appearance were observed regularly. Even spaces were marked on the outside of the test samples and the r e s u l t ing layers were analyzed at d i f f e r e n t times. Analysis was as follows: Water was t i t r a t e d with Karl Fischer reagent using a Metrohm Herisau t i t r i m e t e r consisting of potentiograph E536, Dosimat E535 and E549. The amount of hydrocarbon was determined from i t s UV spectrum with a Perkin-Elmer 522 spectrophotometer. Water, hydrocarbon, and pentanol were vaporised i n a vacuum oven, leaving SDS as the remainder. The pentanol content was obtained as the balance, and checked using gas chromatograph-2500. Results The microemulsion regions for d i f f e r e n t conditions are given i n F i g -

In Surfactant-Based Mobility Control; Smith, D.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.


110

SURFACTANT-BASED MOBILITY CONTROL

ures 1A-D. The t y p i c a l triangular region found with no s a l t present, Fig. 1A, i s shrunk and the water s o l u b i l i z a t i o n maximum moved towards higher surfactant/cosurfactant r a t i o s with increased s a l t content (Figs. 1B-C). Addition of hydrocarbon caused a reduction i n the maximum water s o l u b i l i z a t i o n (Fig. ID) a l l i n accordance with e a r l i e r results (18). The d i f f u s i o n experiments for the nonsalt compositions (Fig. IE) showed a fast e q u i l i b r a t i o n of the surfactant concentration with equal concentration of surfactant i n the entire system after 30 days at the lowest surfactant/(cosurfactant + surfactant) weight r a t i o , 0.14, F i g . 2A. Thereafter the concentration i n the lower part was higher than i n the upper part, a fact that i s to be viewed against the former low cosurfactant concentration, F i g . 2B, and i t s high water content, F i g . 2C. The increase i n water content i n the upper layers ceased after 20 days, F i g . 2C, at the time when the l i q u i d c r y s t a l began to form i n layer 6, F i g . 3. During the f i r s t 7 days the aqueous solution was turbid and an interface appeared within the o i l phase, F i g . 3. This interface moved upwards i n the o i l phase and disappeared after 36 days. With increased surfactant/(cosurfactant + surfactant) r a t i o (0.22), the l i q u i d c r y s t a l was formed immediately and the interface in the o i l layer now lasted only 12 days, (Fig. 4). The formation of a l i q u i d c r y s t a l impeded the transport of surfactant to the lower part, F i g . 5A. In this case, the surfactant concentration remained lower i n the bottom layers during the entire duration of the experiment; more than 2 months. The transport of cosurfactant to lower parts, F i g . 5B, and water from the layers below the l i q u i d c r y s t a l , Fig. 5C, were not influenced to a great degree by the enhanced amount of l i q u i d c r y s t a l . For the highest surfactant/(cosurfactant + surfactant) r a t i o (0.35), the l i q u i d c r y s t a l also formed early, F i g . 6, i n layers 5 and 6. This resulted i n the concentration changes being focused towards the bottom layers; the higher reservoir of surfactant and cosurfactant i n the top layers resulted i n small changes of their concentrations, Figs. 7A-C. The slowest process was the disappearance of the birefringence; a time of 9 months was needed for that to happen, F i g . 6. In the system with 0.5 M NaCl, F i g . 8, the series with the lowest surfactant/cosurfactant r a t i o showed an i n i t i a l uptake of between 50 and 60% of the water during the f i r s t 15 days followed by an extremely slow period (100 days) during which the remaining water was absorbed into the microemulsions. No l i q u i d crystals were observed. The samples with the surfactant/(cosurfactant + surfactant) weight r a t i o equal to 0.35 showed an i n i t i a l formation of l i q u i d c r y s t a l at the interface l a s t i n g approximately 10 days, Figs. 9A,B. The l i q u i d c r y s t a l was present irrespective of whether a l l the sodium chloride was i n the water or distributed i n equal concentration i n the two o r i g i n a l layers. The water volume was reduced faster for the microemulsion containing s a l t than that without s a l t when contacted with water containing s a l t . (Cfr F i g . 9A and F i g . 9B; F i g . 4A and F i g . 4B). The absence of s a l t gave a huge region of l i q u i d crystals l a s t ing more than 80 days, F i g . 10. It i s interesting to notice that the presence of the huge l i q u i d c r y s t a l l i n e layer had but l i t t l e influence on the concentration changes with time, (Cfr Figs. 11A-C



6.

FRIBERG ET AL.


111

Figure 1A. The s o l u b i l i t y region f o r the pentanol solution i n the system: Water, sodium dodecyl sulfate (SDS) and pentanol.




112

Figure ID. Part of the i s o t r o p i c l i q u i d solutions i n the system: Water, sodium dodecyl sulfate and pentanol/t-butylebenzene solution at a 1/1 weight r a t i o .


6. FRIBERG ET AL.


113


PENTANOL

SDS

WATER

Figure IE. Compositions at points 1 to 3 were layered on water i n amounts to give f i n a l combined compositions at the l e f t end-points of the dashed l i n e s .

ω Q ω

0

3

6

9

12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 TIME

DAYS

S O S * OF EVERY L A Y E R AT POINT 1 in

FIG.1E

Figure 2A. The concentration of sodium dodecyl sulfate i n layers versus time (Composition 1, F i g . IE). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y in the upper part of layer 5.


72


114


TIME

DAYS

P E N T A N O L * O F EVERY LAYER AT POINT

1

in F I G . 1 E

Figure 2B. The concentration of pentanol i n layers versus time (Composition 1, F i g . IE). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the upper part of layer 5.

0 1 0

ι

1

i

3

6

9

I

I

1

I . I

1

1

1

I

1

I

I

1

1

1

I

I

I

I

I

12 15 18 21 24 27 3 0 3 3 3 6 3 9 42 4 5 4 8 51 54 5 7 6 0 6 3 6 6 6 9 TIME

DAYS

WATER X OF EVERY LAYER AT P O I N T

1 in F I G . 1 E

Figure 2C. The concentration of water i n layers versus time (Composition 1, F i g . IE). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the upper part of layer 5.


.J

72

6. FRIBERG ET AL.

115

Temporary Liquid Crystah in Microemulsions


LAYER

40 point

50 DAYS

60

70

80

200

1 in F I G . 1 E

Figure 3. After layering the composition at point 1, F i g . IE on water the interface was found r i s i n g upward i n the W/0 microemulsion (A,B,C). After 20 days a biréfringent layer was formed i n the aqueous part slowly disappearing i n 200 days. LAYER

LU

Έ z> -I

Ο >

50 TIME point

300

DAYS 2 in F I G . 1 E

Figure 4. After layering the composition at point 2, F i g . IE on water the interface was found r i s i n g upward i n the W/0 microemul sion (A,B,C). The biréfringent layer i n the aqueous phase was formed immediately and lasted more than 300 days.



116

SURFACTANT-BASED MOBILITY C O N T R O L

Figure 5A. The concentration of sodium dodecyl sulfate i n layers versus time (Composition 2, F i g . IE). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y in the middle of layer 4.

Figure 5B. The concentration of pentanol i n layers versus time (Composition 2, F i g . IE). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the middle of layer 4.


FRIBERG ET AL.

117


100

I

I

I

I

I

I

ι

ι

ι

ι

ι

1

ι

ι

90 80


70

0

3

6

9

12 15 18 21 24 27 30 3 3 3 6 3 9 42 45 48 51 54 57 60 6 3 6 6 6 9 72 TIME

DAYS

WATER* O F EVERY LAYER AT POINT 2

in F I G . 1 E

Figure 5C. The concentration of water i n layers versus time (Composition 2, F i g . IE). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the middle of layer 4. LAYER

ο LU CD

Z>

/ 4

-J

Ο >

oil

phase

ο

27C TIME

DAYS

p o i n t 3 in F I G . 1 E

Figure 6. A biréfringent layer was formed i n the aqueous part immediately, slowly disappearing i n 270 days. The interface was o r i g i n a l l y i n the lower part of layer 5.




118

0

3

6

9

12 15 18 21 2 4 2 7 3 0 3 3 3 6 3 9 4 2 4 5 4 8 51 5 4 5 7 6 0 6 3 6 6 6 9 TIME

72

DAYS

S D S % O F E V E R Y L A Y E R A T POINT 3 in FIG.1E

Figure 7A. The concentration of sodium dodecyl sulfate i n layers versus time (Composition 3, F i g . IE). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y in the middle of layer 5. 70

0

3

6

9

12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 6 0 6 3 66 6 9 TIME

DAYS

P E N T A N O L * OF EVERY LAYER A T POINT 3

in F I G . 1 E

Figure 7B. The concentration of pentanol i n layers versus time (Composition 3, F i g . IE). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the middle of layer 5.


72


6. FRIBERG ET AL.

0

I 0

1

I

I

3

6

9

119


1—I

12

1

15

I

I

I

18 21

24

27

I

I

30 33 36

I

I

39

TIME

I

I

I

I

42 45 48 51

1

I

I

54 57 60 63

I

I

I

66

69

DAYS

WATER* OF EVERY LAYER

AT P O I N T 3 in

FIG.1E

Figure 7C. The concentration of water i n layers versus time (Composition 1, F i g . IE). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the lower part of layer 5.

Figure 8. The pentanol solution region i n the system 0.5 M NaCl aqueous solution, sodium dodecyl sulfate (SDS) and pentanol. The dashed l i n e shows the corresponding area i n the system with the water (Fig. 1A).


I 72

120

SURFACTANT-BASED MOBILITY CONTROL LAYER

LU

oil phase

D -J

containing NaCI

2

Ο

>

2


interface

water

phase 10

20

30

40

TIME point

50

"60-

70

eb

DAYS ρ in F I G . 8 ( s o l i d line )

Figure 9A. After layering the composition at point P, F i g . 8 on water a biréfringent layer was formed i n the aqueous part after 20 days, disappearing i n 8 days point P. I t was replaced by a f a i r l y extensive i s o t r o p i c l i q u i d middle phase, which was gradually reduced to zero i n 52 days. The aqueous phase was slowly depleted l a s t i n g more than 150 days. LAYER

2 3

Ο

>

10

20

30

40

TIME point Ρ in F I G . 8

50

60

70

80

DAYS ( from d a s h e d line to solid line )

Figure 9B. With no e l e c t r o l y t e i n the pentanol solution the behavior was similar to the system i n F i g . 9A.


150

6. FRIBERG ET AL·


111

LAYER

CO' LU


2 -J

4 oil phase NO NaCI interface

5

TIME

DAYS

point Ρ in F I G . 8 ( d a s h line )

Figure 10. Without e l e c t r o l y t e a biréfringent layer developed i n the aqueous phase.

SDSX OF EVERY LAYER AT POINT Ρ in F I G . 8 < solid line )

Figure 11A. The concentration of sodium dodecyl sulfate i n layers versus time (Composition P, F i g . 8). Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y in the upper part of layer 6.


122


70 60

' ^ -Α

Β

η

^—z^riî—

'

2

3

"

il

«—

-ψ

5

V


20

J

10 0 (j) 0

^· -—e~

Θι 5

10

—

— "ι 15 TIME

— θ -

°" 1

20

—

1

25

1

—

30

1

35

DAYS

P E N T A N O L * OF EVERY LAYER A T POINT Ρ in F I G . 8 ( solid line )

Figure 11B. The concentration of pentanol i n layers versus time (Composition P, F i g . 8 ) . Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the upper part of layer 6.

10 h

10

15 TIME

20

25

30

DAYS

WATER X OF EVERY L A Y E R A T POINT Ρ

in F I G . 8 ( solid line )

Figure 11C. The concentration of water i n layers versus time (Composition P, F i g . 8 ) . Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the upper part of layer 6.


35


6. FRIBERG ET AL.


123

and Figs. 12A-C) except for the fact that the pentanol transport into the NaCl aqueous solution (Fig. 11B) was slower than i n to pure water (Fig. 12B). For the 1 M NaCl system the s o l u b i l i t y region was further reduced, F i g . 13, and the water s o l u b i l i z a t i o n maximum found at even higher surfactant/cosurfactant r a t i o . The series with the lower r a t i o s of surfactant to cosurfactant showed an uptake of the aqueous solution somewhat similar to the series i n the system with 0.5 M NaCl. The series with the surfactant/(cosurfactant + surfactant) r a t i o equal to 0.4 gave an i n i t i a l l i q u i d c r y s t a l formation l a s t i n g for 2-3 days folllowed by a middle phase l a s t i n g a longer time. The l i q u i d c r y s t a l l i n e and the middle phase layer were both more pronounced for the sample with i n i t i a l s a l t concentration equal i n the water and i n the microemulsion, F i g . 14A, than for the sample with a l l the s a l t i n the water, F i g . 14B. The hydrocarbon system was combined with water to form the W/0 microemulsions marked i n F i g . 15. The surfactant/(cosurfactant + surfactant) weight r a t i o 0.25 gave a l i q u i d c r y s t a l with i n i t i a l fast extension f o r three days followed by a new fast growth between 10 and 17 days and a subsequent decline to zero i n 40 days, F i g . 16. These changes were reflected i n the concentration changes i n the layers around the l i q u i d c r y s t a l (Figs. 17A-D). The water concentration showed a rapid growth i n layer 3, the f i r s t three days caused by a reduction of the surfactant, cosurfactant and the hydrocarbon content. The conditions i n the series with surfactant/(cosurfactant + surfactant) r a t i o (0.30), F i g . 18, were similar but the duration of the l i q u i d c r y s t a l l i n e phase was shorter. The concentration changes were also very similar, Figs. 19A-C. Discussion The results gave direct information about the reason for the appearance of the l i q u i d c r y s t a l when a water-poor W/0 microemulsion i s contacted with water. They also explain the appearance of an i n t e r face within the microemulsion layer, a not so normal phenomenon considering the fact that the phases above and below this interface i s a W/0 microemulsion with similar composition. The formation of a l i q u i d c r y s t a l was influnced by d i l u t i o n of the W/0 microemulsion by hydrocarbon. The results showed that layers of l i q u i d c r y s t a l s are formed also i n the presence of hydrocarbon and l a s t i n g a considerable time, 40 days, F i g . 16. In comparison, the non-hydrocarbon systems gave more extended duration, the composition in F i g . 4 would give a l i q u i d c r y s t a l l a s t i n g at least two years. Another important factor i s the s a l i n i t y of the aqueous phase. The presence of high concentrations of e l e c t r o l y t e usually destabil i z e s a l i q u i d c r y s t a l l i n e phase (18) of a charged surfactant and a long chain alcohol; the present results show the temporary l i q u i d crystals to exist only for a few days, when the water was 1 M or 1.7 M NaCl solution, Figs. 14A,B. After that time the l i q u i d c r y s t a l was replaced by an isotropic l i q u i d middle phase (2,3). The fundamental phenomenon of interest i s the explanation for the appearance of the l i q u i d c r y s t a l . It i s provided by the diagrams showing concentration changes i n the different layers versus time


124



30 r

1

1

1

TIME

1

1

Γ

DAYS

SDSX OF EVERY LAYER A T POINT Ρ in F I G . 8 (dashed line)

Figure 12A. The concentration of sodium dodecyl sulfate i n layers versus time (Composition P, F i g . 8; No e l e c t r o l y t e ) . Layer 1 i s the top part of the sample, layer 7 the bottom part. The i n t e r face was i n i t i a l l y i n the upper part of layer 6. 70

,

—

TIME

DAYS

P E N T A N O L * O F EVERY LAYER A T POINT

Ρ

in F I G . 8

(from dashed line

to solid line )

Figure 12B. The concentration of pentanol i n layers versus time (Composition P, F i g . 8; No e l e c t r o l y t e ) . Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the upper part of layer 6.



6. FRIBERG ET AL.


125

ι Q

I

1

I

I

I

0

5

10

15

20

TIME

I

'

25

30

DAYS

WATER* O F EVERY L A Y E R AT P O I N T Ρ in F I G . 8 (from dashed line to s o l i d line )

Figure 12C. The concentration of water i n layers versus time (Composition P, F i g . 8; No e l e c t r o l y t e ) . Layer 1 i s the top part of the sample, layer 7 the bottom part. The interface was i n i t i a l l y i n the upper part of layer 6. PENTANOL

WATER 1 M NaCl

SDS

Figure 13. The pentanol solution region i n the system 0.5 M NaCl aqueous solution, sodium dodecyl sulfate (SDS) and pentanol. The dashed l i n e shows the corresponding area i n the system with water (Fig. 1A).


35

126


2 Ο

oil phase o|

containing NaCl


interface

TIME

DAYS

point Q in FIG. 13 (solid line )

Figure 14A. After layering the composition at point Q, F i g . 13, on 1 M NaCl a biréfringent layer l a s t i n g 3 days was found at the top of the aqueous phase. It was replaced by a f a i r l y extensive i s o t r o p i c l i q u i d middle phase, which was gradually reduced to zero i n 40 days. The aqueous phase was slowly depleted l a s t i n g more than 105 days. LAYER

50 TIME

60

70

80

DAYS

point Q in FIG. 13 (from dashed line to solid tine)

Figure 14B. After layering the composition at point Q, F i g . 13, on 1.71 M NaCl a biréfringent layer l a s t i n g 8 days was found at the top of the aqueous phase. It was replaced by a f a i r l y extensive i s o t r o p i c l i q u i d middle phase, which was gradually reduced to zero i n 37 days. The aqueous phase was slowly depleted l a s t i n g more than 105 days.


6. FRIBERG ET AL.



PENTANOL & f-BUTYLBENZENE(l Ί

WATER

127

w)

SDS

Figure 15. The s o l u b i l i t y region for the W/0 microemulsion (top) and part of the 0/W microemulsion region i n the system water, sodium dodecyl sulfate, pentanol and t-butylbenzene.

LAYER

m

ZD

-J

Ο

>

point

1 in F I G .

15

Figure 16. After layering the W/0 microemulsion composition i n point 1, F i g . 15, on water to give a t o t a l composition at the end-point of the dashed l i n e from point 1 a biréfringent layer developed i n the o i l phase reaching a maximum i n 18 days and depleted i n 40 days.



128


0 I 0

· 3

· 6

• 9

• 12 TIME

WATER*

' IS

' 18

' 21

» 24

DAYS

OF EVERY LAYER AT POINT 1

in

FIG.15

Figure 17A. The water concentration at d i f f e r e n t heights f o r the conditions i n F i g . 16. The interface was i n i t i a l l y between layers 3 and 4.

Ο

3

6

9

12 TIME

15

18

21

OAYS

SOSX OF EVERY LAYER AT POINT 1 in F I G . 15

Figure 17B. The sodium dodecyl sulfate concentration at d i f f e r e n t heights f o r the conditions i n F i g . 16. The interface was i n i t i a l l y between layers 3 and 4.


24

FRIBERG ET AL.

Temporary Liquid Crystals in Microemuhions

129

70


00 ' 90

-

40

·

0

3

6

9

12 TIME

HYDROCARBON*

15

18

21

DAYS

OF EVERY LAYER point

1 in F I G . 15

Figure 17C. The hydrocarbon concentration at d i f f e r e n t heights for the conditions i n F i g . 16. The interface was i n i t i a l l y between layers 3 and 4.

70 60

50

V

TIME PENTANOL*

DAYS

OF EVERY LAYER AT POINT

1 in F I G . 15

Figure 17D. The pentanol concentration at d i f f e r e n t heights f o r the conditions i n F i g . 16. The interface was i n i t i a l l y between layers 3 and 4.


24

130


ο

LAYER

Ό -

1 Ο ω

2

ο interface CO

w a t £ s r

^ ™

3 4

ο •

Temporary Liquid Crystals in Microemulsion Systems - American

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