Surfactant Association Structures - ACS Symposium Series (ACS

1

Downloaded by UNIV OF CALIFORNIA SAN FRANCISCO on February 18, 2015 | http://pubs.acs.org Publication Date: February 12, 1982 | doi: 10.1021/bk-1982-0177.ch001

Surfactant A s s o c i a t i o n Structures STIG E. FRIBERG and TONY FLAIM University of Missouri—Rolla, Department of Chemistry, Rolla, MO 65401 The phase regions for micellar solutions and lyotropic liquid crystals form a complicated pat tern in water/amphiphile/hydrocarbon systems. The present treatment emphasizes the fact that they may be considered as parts of a continuous solubility region similar to the one for water/short chain amphiphilic systems such as water/ethanol/ethyl acetate. Hence the different phases may be visualized as a series of association structures with increas ing complexity from the monomeric to the liquid crystalline state. The transfer from the monomeric state to the inverse micellar structure is discussed for two special cases and it is shown that packing constraints may prevent the formation of inverse micelles. Instead a liquid crystalline phase may form. The surfactant association structures have a long history of research ranging from the McBain introduction of the aqueous micellar concept CL) over the interpretation of micellization as a critical phenomenon'-=.'-2/ to the analysis of the structure of lyo tropic liquid crystals^) and the comprehensive picture of the phase relations in water/surfactant/amphiphile systems. Cl) These studies have emphasized the relation between the association structures in isotropic liquid solutions and the liquid crystal line phases. Parallel extensive investigations in crystalline/ liquid crystalline lipid structures(A>Z) have provided important insight in the mechanisms of the associations. The thermodynamics of these systems have been extensively discussed in recent years including the m i c e l l i z a t i o n , ' the liquid crystalsCi2) and inverse micellization. In addition the more general problem of the stability of microemulsions has been extensively covered.(λ!τ1§) 0097-6156/82/0177-0001$05.00/0 © 1982 American Chemical Society In Inorganic Reactions in Organized Media; Holt, S.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

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INORGANIC REACTIONS IN

ORGANIZED M E D I A

T h i s a r t i c l e w i l l , i n a d d i t i o n to a short d e s c r i p t i o n of the e s s e n t i a l features of s u r f a c t a n t systems i n general, concentrate on the energy c o n d i t i o n s i n premicellar'aggregates, the t r a n s i t i o n p r e m i c e l l a r aggregates/inverse m i c e l l a r s t r u c t u r e s and the d i r e c t t r a n s i t i o n premicellar aggregates/lyotropic l i q u i d c r y s t a l s .


Surfactant

Systems - A Word of Caution

The i n v e r s e m i c e l l a r s o l u b i l i t y areas i n systems of water, s u r f a c t a n t s and a t h i r d amphiohilic substance f r e q u e n t l y are of a shape according to F i g , 1.C1Z/ Such shapes are a l s o found i n W/0 microemulsions » ϋ ) when water s o l u b i l i t y i s p l o t t e d against cosurfactant/surfactant f r a c t i o n . I t i s tempting to evaluate t h i s s o l u b i l i t y curve as showing a maximum of water s o l u b i l i t y at the apex p o i n t . I t i s e s s e n t i a l to r e a l i z e that any thermodynamic e v a l u a t i o n of t h i s s o l u b i l i t y "maximum" with standard reference c o n d i t i o n s i n the form of the three pure components i n l i q u i d form i s a f u t i l e exercise. The complete phase diagram, F i g . 2, shows the "maximum" of the s o l u b i l i t y area to mark only a change i n the s t r u c t u r e of the phase i n e q u i l i b r i u m with the s o l u b i l i t y r e g i o n . The maximum of the s o l u b i l i t y i s a r e f l e c t i o n of the f a c t that the water as e q u i l i b r i u m body i s replaced by a l a m e l l a r l i q u i d c r y s t a l l i n e phase. Since t h i s phase t r a n s i t i o n obviously i s more r e l a t e d to packing c o n s t r a i n t s ' — ' than enthalpy of f o r m a t i o n ^ — ' a view of the d i f f e r e n t phases as one continuous r e g i o n such as i n the short chain compounds water/ethanol/ethyl a c e t a t e , F i g . 3, i s realistic. The three phases i n the complete diagram, F i g . 2, may be perceived as a continuous s o l u b i l i t y area with d i f f e r e n t pack ing c o n d i t i o n s i n d i f f e r e n t p a r t s ( F i g . 4 ) . T h i s means that the phase changes observed have comparatively l e s s importance f o r the thermodynamics of the system. On the other hand, the changes and m o d i f i c a t i o n s of the a s s o c i a t i o n s t r u c t u r e s w i t h i n the i s o t r o p i c l i q u i d hydrocarbon or a l c o h o l phase pose a s e r i e s of i n t e r e s t i n g problems. Some of these have r e c e n t l y been t r e a t e d i n review a r t i c l e s by F e n d l e r ' — ' who focussed on s u r f a c t a n t i n t e r - a s s o c i a t i o n emphasizing consecutive e q u i l i b r i a and t h e i r thermodynamics. The f o l l o w i n g d e s c r i p t i o n w i l l focus on the i n t e r m o l e c u l a r i n t e r a c t i o n between d i f f e r e n t kinds of molecules and the importance of these i n t e r a c t i o n s f o r the " i n v e r s e " a s s o c i a t i o n s t r u c t u r e s . I t should be emphasized that these s t r u c t u r a l changes w i t h i n a one-phase r e g i o n may change the k i n e t i c s of a chemical r e a c t i o n i n a pronounced manner. As an example may be mentioned the c a t a l y t i c e f f e c t of inverse m i c e l l e s on e s t e r h y d r o l y s i s . F i g . 5 i s from the f i r s t p u b l i c a t i o n o n t h i s subject. I t c l e a r l y shows the l a c k of c a t a l y t i c e f f e c t by the p r e m i c e l l a r aggregates and the sudden increase of h y d r o l y s i s r a t e i n the concentration range where the i n v e r s e m i c e l l e s begin being formed.

In Inorganic Reactions in Organized Media; Holt, S.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

FRIBERG A N D F L A i M

Surfactant Association Structures


C

H0

H

6 6

C (EO^

2

12

Figure 1. The solubility area of water in a hydrocarbon (C H ) pentafethylene glycol) dodecyl ether (C [EO] ) solution at 30°C. Key: IM, inverse micellar solution. 6

lt

H0 2

e

s

C (EO) 12

5

Figure 2. The phase diagram water/benzene/penta(ethylene glycol) dodecyl ether at 30°C. Key: IM, inverse micellar solution; LLC, lamellar liquid crystal; and unmarked, aqueous micellar solution.


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INORGANIC REACTIONS I N ORGANIZED M E D I A


Ε TO AC

H0 2

Figure 3.

Figure 4.

ETOH

The phase diagram water/ethanol (ETOH)/ethyl acetate (ETOAC).

The similarity of Figure 3 to Figure 4 is seen if the maximum solubility of water is emphasized.



FRIBERG AND FLAIM


TO

20

30

water, wt.7o

40"

Figure 5. The premicellar aggregates (< 12% water) do not catalyze the hydrolysis of an ester (22).



6


Two s o l u t i o n s t o i l l u s t r a t e these s t r u c t u r a l changes w i t h i n one phase were chosen w i t h emphasis both on t h e i r p r a c t i c a l importance and on the pronounced d i f f e r e n c e i n behavior brought about by a small d i f f e r e n c e i n composition. The two l i q u i d s chosen a r e both soap/water s o l u t i o n s i n a) an a l c o h o l and b) a c a r b o x y l i c a c i d . The a l c o h o l s o l u t i o n s form the b a s i s f o r the W/0 microe m u l s i o n s ^ — ' and the c a r b o x y l i c a c i d s o l u t i o n s show a pronounced d i f f e r e n c e i n p r o p e r t i e s which merit an e v a l u a t i o n o f the i n t e r molecular f o r c e s between the solvent and the s o l u t e . The primary d i f f e r e n c e i s i n the minimum concentration o f water that i s r e q u i r e d to form the s o l u t i o n . Minimum Water Content The two i n v e r s e m i c e l l a r s o l u t i o n s w i l l f i r s t b r i e f l y be described followed by an e v a l u a t i o n o f the a v a i l a b l e experimental and t h e o r e t i c a l information. The Sodium Carboxylate/Carboxylic A c i d System. This system has been i n v e s t i g a t e d using IR and NMR^?3) showing the extremely strong hydrogen bonds present. I t appeared evident e a r l y t h a t the strong hydrogen bonds between i o n i z e d and nonionized c a r b o x y l i c groups were r e s p o n s i b l e f o r the s t a b i l i t y of the 4 acid:2 soap complex\±z/ but no information could be obtained on the energy f o r formation of the complex nor could the s t a b i l i t y be based on a thermodynamic c a l c u l a t i o n . An answer has been given a f t e r c a l c u l a t i o n s of the binding energies using the CNDO/2 semi-empirical approach'-=2y to quantum mechanical c a l u l a t i o n s . The r e s u l t s i l l u s t r a t e d the importance both o f the hydrogen bond and the carbonyl/sodium i o n l i g a n d bond of the proposed s t r u c t u r e . The values f o r the hydrogen bond strength (19.5 Kcal/mole, 82 kJ/mole) compared w e l l with the g e n e r a l l y accepted values f o r other ion/molecule systems. C±£) In a d d i t i o n to the hydrogen bond the 4:2 molecular compound i s s t a b i l i z e d by the a c i d carbonyl/sodium l i g a n d bond, 36.1 kcal/mole (151 kJ/mole). The c a l c u l a t i o n s — ' i n v o l v i n g a thermodynamic c y c l e from the s o l i d c r y s t a l l i n e soap and the l i q u i d a c i d as references s t a t e s showed the 4:2 complex t o be s t a b l e even i n the gaseous s t a t e . The t r a n s i t i o n from gaseous t o l i q u i d s t a t e should give f u r t h e r s t a b i l i z a t i o n t o the s t r u c t u r e . The e x c e l l e n t s t a b i l i t y o f the compound was i l l u s t r a t e d by the f a c t that d i l u t i o n s t o a compos i t i o n of the 7% sodium octanoate/octanoic a c i d , 93% by weight C C L 4 , gave no change of the s t r u c t u r e . These c o n d i t i o n s are*conspicuously i n c o n t r a s t with those i n the c a r b o x y l a t e / a l c o h o l system. The C a r b o x y l a t e / A l c o h o l System. A comparison between d i f f e r e n t a l c o h o l s o l u b i l i t y areas w i t h d i f f e r e n t s u r f a c t a n t s and water^— r e v e a l s the f a c t that a minimum water/surfactant r a t i o


1.

FRiBERG A N D F LAI M


7


i s necessary i n order to ensure s o l u b i l i t y of the s u r f a c t a n t i n the a l c o h o l . This i s i n c o n t r a s t to the behavior of a l i q u i d c a r b o x y l i c a c i d that w i l l d i s s o l v e a soap w i t h no water p r e s ent(29) ( F i g . 6). The d i f f e r e n c e i s pronounced. I n an a l c o h o l s o l u t i o n a minimum of approximately s i x water molecules a r e required per soap t o b r i n g i t i n t o s o l u t i o n . A l i q u i d c a r b o x y l i c a c i d w i l l d i s s o l v e the soap without water to a soap/acid molecular r a t i o of 1/2. I t appears reasonable to evaluate these d i f f e r e n c e s from terms o f intermolecular f o r c e s . These f o r c e s , the strong hydrogen bonds and l i g a n d bonds t o the metal i o n w i l l be t r e a t e d i n the following section. Experimental Information. The review by Ekwall(5) o f f e r s a whole s e r i e s o f phase diagrams which a l l show s i m i l a r behavior. In order to d i s s o l v e an a n i o n i c s u r f a c t a n t with a sodium counter ion i n an a l c o h o l a minimum water/surfactant molar r a t i o of about s i x i s needed to achieve s o l u b i l i t y . The corresponding r a t i o f o r the potassium i o n i s three. At the same time i n v e s t i g a t i o n s using l i g h t s c a t t e r i n g , e l e c t r o n microscopy, p o s i t r o n a n n i h i l a t i o n , d i e l e c t r i c i t y and transport properties(19,30-34) i n d i c a t e d the s u r f a c t a n t molecules not to be involved i n a s s o c i a t i o n s to c o l l o i d a l s i z e aggregates at these low water contents. The low l i g h t s c a t t e r i n g i n t e n s i t y r a t h e r p o i n t s to the s u r f a c t a n t molecules not to be i n t e r associated (Fig. 7 ) . An approximate thermodynamic evaluation(27) based on l i q u i d water and c r y s t a l l i n e sodium octanoate as reference s t a t e s has r e c e n t l y evaluated the energy c o n d i t i o n s i n the p r e m i c e l l a r aggregate. The c a l c u l a t i o n s e s s e n t i a l l y were concerned w i t h the f r e e energy of a gaseous soap/water complex. No attempt was made to evaluate the chemical p o t e n t i a l changes i n any of the components when d i s s o l v e d i n the pentanol. Accepting the f a c t s that the c a l c u l a t i o n s may be considered a zero order approach, the r e s u l t s a r e i l l u s t r a t i v e o f the reason f o r the s t a b i l i t y o f these small aggregates. The c a l c u l a t i o n s included heat o f evaporation of the s u r f a c t a n t , heat of evaporat i o n o f water and the f r e e energy a s s o c i a t i o n i n the gaseous phase. The enthalpy of the l a t t e r was c a l c u l a t e d using the CDNO/2 approach(25) modified f o r l a r g e r aggregates CDNO/2 has a proven record f o r accuracy i n d e s c r i b i n g the energy o f i n t e r a c t i o n f o r water c l u s t e r s around metal ions i n aqueous s o l u t i o n s . (36,37) The entropie c o n t r i b u t i o n due to the d i f f e r e n t s p a t i a l arrangements of the p a r t i c l e s was c a l c u l a t e d using the l i q u i d volume according t o Ruckenstein(13) and Reiss.(38) The f o l l o w i n g model was employed. The water molecules were c o n s e c u t i v e l y entered i n t o a r e g u l a r octahedron around the sodium ion with the two f i r s t water molecules hydrogen bonded t o the carboxylate group. Water molecules i n excess of the s i x f i r s t



8

INORGANIC REACTIONS IN ORGANIZED M E D I A

fraction, S/(S+A) Figure 6. The solubility of water (weight percent of total) in sodium octanoate (S)foctanoic acid (A) ( ) and sodium octanoate (S)/octanol (A) ( ) mixtures (weight fraction).



1. FRIBERG A N D F L A I M


9

80 OA

Inverse micelle region Strong increase of Scattering intensity

600-1

400 -I

20 CM Submicellar region Low scattering intensity

10

Pure benzene

30

Concentration

(%Η θ)

50

2

Figure 7. At low water content (< 35% by weight) the water is not involved in colloidal association structures in a pentanol/potassium oleate (weight ratio 3.0) solution.



10


ORGANIZED M E D I A

ones were hydrogen bonded forming an outer s h e l l to the primary octahedron. The r e s u l t s are given i n F i g . 8.C!LZ) It i s obvious that the r e s u l t s depend on the s p e c i f i c model chosen and that g r e a t e s t care should be e x e r c i s e d when c o n c l u sions are drawn. However, the f o l l o w i n g remarks about the r e s u l t s may be j u s t i f i e d . The h i g h h y d r a t i o n energy f o r the f i r s t added water molecules are p r i m a r i l y r e s p o n s i b l e f o r the thermodynamic s t a b i l i t y of these p r e m i c e l l a r aggregates. The c a l c u l a t i o n s show a minimum of f i v e water molecules to be necessary f o r the s t a b i l i t y of the gaseous complex. The agreement with experimental v a l u e s , 5.5-6 ^0/ soap,\i/ i s e x c e l l e n t . T h i s coincidence i s to some extent f o r t u i t i o u s , but the s t r o n g negative shape of the f r e e energy curve (Fig. 8) s u b s t a n t i a t e s the c l a i m of the main d r i v i n g f o r c e being the high heat of h y d r a t i o n f o r the i n i t i a l l y bound water mole cules. Experimental r e s u l t s ^ — > — ~ — ^ show a maximum of ten water molecules per soap molecule to be s t a b l e f o r t h i s monomeric specimen. According to the c a l c u l a t i o n s and to the chosen model the s t a b i l i t y ends a t t h i r t e e n water molecules per soap molecule g i v i n g a p o s i t i v e f r e e energy and i n s t a b i l i t y f o r t h i s monomeric specimen a t higher water contents. Again the general trend supports the r o l e of a l a r g e h y d r a t i o n energy as the s t a b i l i z i n g factor. Stable s t r u c t u r e s a t h i g h water contents could be l i q u i d water, s p h e r i c a l i n v e r s e m i c e l l e s or l i q u i d c r y s t a l s with l a m e l l a r or " i n v e r s e hexagonal" s t r u c t u r e . The t r a n s i t i o n to the two l a s t s t r u c t u r e s w i l l be discussed i n the next s e c t i o n . P r e m i c e l l a r Aggregates/Inverse

Micelles/Liquid Crystals

The c a l c u l a t i o n s presented i n the preceeding s e c t i o n agree w e l l w i t h experimental evidence. The l i g h t s c a t t e r i n g s t u d i e s of the system water/potassium oleate/pentanolQJO show a t r a n s i t i o n from p r e m i c e l l a r aggregates to i n v e r s e m i c e l l e s a t a water/soap molecular r a t i o of 10 and an alcohol/soap molecular r a t i o of ten and higher. The s e r i e s with the higher soap content, alcohol/soap molecular r a t i o 5.5, d i d not show m i c e l l i z a t i o n ; i n s t e a d a l a m e l l a r l i q u i d c r y s t a l was formed when a s s o c i a t i o n i n excess of the p r e m i c e l l a r aggregates took p l a c e . T h i s phenomenon can be understood i n a q u a l i t a t i v e manner u s i n g semi-empirical thermo dynamics. (8>39) The chemical p o t e n t i a l of an a s s o c i a t e d amphiphile, μ , i s taken a s ® n

μ

ο n

2

, 2ue D ^ = γ·a + — - — + g a E

i n which γ i s the i n t e r f a c i a l t e n s i o n at the i n t e r f a c e of the a s s o c i a t i o n s t r u c t u r e , a i s the amphiphile c r o s s - s e c t i o n a l area



FRIBERG A N D F L A i M


moles H o/mole soap 2

Figure 8. Free-energy difference from solid crystalline sodium octanoate and liquid water for a (mono) sodium octanoate/water molecular compound with different numbers of water molecules.


12


ORGANIZED M E D I A

being i n contact with the water, e the e l e c t r o n i c charge, D i s the Debye d i s t a n c e , E the d i e l e c t r i c constant and g the energy to t r a n s f e r the hydrocarbon c h a i n from water to the hydrophobic part of the a s s o c i a t i o n s t r u c t u r e . T h i s approach can be used to g i v e c r i t i c a l m i c e l l i z a t i o n concentrations as w e l l as s i z e d i s t r i b u t i o n s of aggregates(8) but i s , of course, unable to d i s t i n g u i s h between d i f f e r e n t forms of the a s s o c i a t i o n s t r u c t u r e s . In order to achieve t h i s packing, r e s t r a i n t s must be introduced.(8) The r e l e v a n t term i s the expression V/ao1c i n which ν i s the volume of the hydrocarbon c h a i n , a i s the c r o s s - s e c t i o n a l area of the amphiphile (assumed constant) and l i s the c r i t i c a l chain l e n g t h (= 90% of the f u l l y extended hydrocarbon c h a i n ) . With these postulates(8) the f o l l o w i n g c o n d i t i o n s may be s t a t e d (Table I ) . The o r i g i n a l c o n t r i b u t i o n ( 8 ) a p p l i e d these c o n d i t i o n s to twophase systems of amphiphile and water. An extension to a t h r e e component system encounters p a r t i t i o n a l problems, s i n c e the exact l o c a t i o n of the t h i r d molecule may not be known. The information about area per head-group a v a i l a b l e i s from low angle X-ray data on l i q u i d c r y s t a l s . E k w a l l ® e a r l y found that the mean area i n a b i n a r y system obeys the r e l a t i o n


a

o

c

S = S Z

g

or

1

log S - log

+ g InZ

i n which S i s area per head-group, i s area per head-group with 1 H2O, Ζ i s number of water molecules per soap and g i s a constant = 0.2. For soap/alcohol combinations(5) g w i l l depend not only on the soap counter i o n but a l s o on the alcohol/soap r a t i o . Further more, when a c e r t a i n alcohol/soap r a t i o i s exceeded (-2 f o r the potassium o l e a t e system) S becomes independent of the water con tent of the l a m e l l a r phase. T h i s c o n d i t i o n a p p l i e s f o r i n v e r s e s t r u c t u r e s and the water/pentanol/potassium o l e a t e i n v e r s e m i c e l l a r system w i l l be examined f o r the s t r u c t u r e determining r a t i o i n Table I. The mean p o l a r head group area i n a water/decanol/potassium o l e a t e system i s approximately 26 A f o r an alcohol/soap molecular r a t i o of 2.1(5). For the soap alone an area of 36.0 was found. Assuming a l i n e a r r e l a t i o n s h i p a value of 22 A2 i s obtained f o r the decanol. This value w i l l be used a l s o f o r the pentanol. The volume, c h a i n l e n g t h and area can now be e s t i m a t e d ® 3

ν = 27.4 + 26.9

(A ) a R

l

c

= 0.9

(1.5 + 1.265

+

7

) ( A

3

)

a



1.

FRIBERG AND FLAIM


TABLE I .

Conditions f o r d i f f e r e n t amphophilic a s s o c i a t i o n s t r u c t u r e s

ν a 1 ο c £ 1/3 ^ *2

Preferred

structure

Aqueous, s p h e r i c m i c e l l e s C y l i n d e r s with p o l a r groups outwards

£ γ> < 1

Bilayers

>, 1

Inverse s t r u c t u r e s


13

14


a

o

36 + 21 R a " 1 + R a


and

the — — — can be c a l c u l a t e d f o r an i n v e r s e m i c e l l a r s o l u t i o n , a 1 The ο c experimental r e s u l t s f o r the water/pentanol/potas sium o l e a t e system (18,19) show that a ρentanol/potassium o l e a t e molecular r a t i o of 5.5 and lower should give a p r e m i c e l l a r aggregate/lamellar l i q u i d c r y s t a l t r a n s i t i o n i n s t e a d of the p r e m i c e l l a r aggregate/inverse m i c e l l e t r a n s i t i o n a t h i g h a l c o h o l / soap r a t i o s . C a l c u l a t i o n of the expression v / a l f o r a pentanol/potassium o l e a t e r a t i o o f 5.5 gives the r e s u l t Q

c

v/a 1 - 0.98 ο c A pentanol/potassium o l e a t e r a t i o of 15 that i s t y p i c a l o f the i n v e r s e m i c e l l a r s o l u t i o n gives the corresponding value 1.02. Formally the two values are s t r a d d l i n g the value v/a l - 1 in the c o r r e c t d i r e c t i o n s , but i t i s obvious that they a r e extremely s i m i l a r and the a p p l i c a t i o n of the zeroth order a p p r o a c h ® to these systems must be viewed with c a u t i o n . The pronounced i n f l u ence o f a p a r t i t i o n of c o s u r f a c t a n t s between the i n t e r f a c e and the organic bulk i s evident. Q

c

Summary I t has been shown that the presence of strong i n t e r m o l e c u l a r f o r c e s may have a d r a s t i c e f f e c t on the s t a b i l i t y of p r e m i c e l l a r aggregates i n i n v e r s e m i c e l l a r systems. The s t a b i l i t y of a c a r b o x y l i c acid/soap p r e m i c e l l a r aggregate was shown to be due to the presence of extremely strong hydrogen and l i g a n d bonds. In a l c o h o l systems the corresponding s t a b i l i z ing energy was the l a r g e heat of h y d r a t i o n of the water molecules forming the f i r s t s h e l l around the counter i o n . The d e s t a b i l i z a t i o n of the p r e m i c e l l a r aggregates a t h i g h water content may g i v e r i s e t o a) s e p a r a t i o n o f l i q u i d water, b) formation of i n v e r s e m i c e l l e s , or c) s e p a r a t i o n o f a l a m e l l a r l i q u i d c r y s t a l . Approximate c a l c u l a t i o n s using the TanfordNinham approach gave c o r r e c t information f o r a model system, but the c r i t i c a l r a t i o appeared too i n s e n s i t i v e to the alcohol/soap r a t i o to be u s e f u l .


1.

FRIBERG AND FLAIM


15

Literature Cited 1. McBain, J. W.; Laing, M. E.; and Titley, A. F. J. Chem. Soc. 115, 1279 (1919). 2. Jones, E. R.; Bury, C. R. Phil. Mag. 4, 1 (1927).


3.

Ekwall, P. Acta Acad. Aboensis (Math et Phys.) 4, 1 (1927).

4. Luzzati, V.; Mustacchi, H.; Skoulios, Α.; Huson, F. Acta. Crystallogr. 13, 660 (1960). 5. Ekwall, P. "Advances in Liquid Crystals" (G.H. Brown, Ed.) Vol. 1, Academic Press, New York (1974) page 1. 6.

Chapman, D. "The Structure of Lipids" Methnen and Co., London (1965).

7. Larsson, K. "Surface and Colloidal Science" (E. Matijevic, Ed.) Vol. 6, John Wiley and Sons (1973) p. 261. 8.

Israelachvili, J. N.; Mitchell, D. J.; Ninham, B. W. J. Chem. Soc. Faraday Trans. II, 72, 1525 (1976).

9. Jönsson, B.; Wennerström, H. J. Colloid Interface Sci., 80, 482 (1981). 10.

Parsegian, V. A. Trans. Faraday Soc., 62, 848 (1966).

11.

Ekwall, P.; Mandell, L . ; Fontell, K. Mol. Cryst., 8, 157 (1969).

12.

Eicke, H. F.; Christen, H. J . Colloid Interface Sci., 46, 417 (1974).

13.

Ruckenstein, E.; Chi, J . C. J. Chem. Soc. Faraday Trans II, 71, 1680 (1975).

14.

Ruckenstein, E. J . Dispersion Sci. Technol., 2, 1 (1981).

15.

Brois, J . ; Bothorel, P.; Clin, B.; Lalanne, P. J. Dispersion Sci. Technol., 2, 67 (1981).

16.

Ninham, B. W.; Mitchell, D. J. J. Chem. Soc. Faraday Trans. II, 76, 201 (1980).

17.

Christenson, H.; Larsen, D. W.; Friberg, S. E. J . Phys. Chem., 84, 3633 (1980).



16

INORGANIC REACTIONS IN ORGANIZED MEDIA

18.

Friberg, S.; Buraczewska, I. Progr. Colloid Polymer Sci., 63, 1 (1978).

19.

Sjoblom, E.; Friberg, S. E. J . Colloid Interface Sci., 67, 16 (1978).

20.

Stenius, P.; Rosenholm, J. B.; Hakala, M. R. "Colloid and Interface Science II," (M. Kerker, Ed.) Academic Press, New York, (1976) p. 397.

21.

Fendler, J. Acc. Chem. Res., 9, 153 (1976); 13, 7 (1980).

22.

Friberg, S. E.; Ahmad, S. I. J. Phys. Chem., 75, 2001 (1971).

23.

Friberg, S. E.; Mandell, L.; Ekwall, P. Kolloid-Z.u.Z. Polymère, 233, 955 (1969).

24.

Söderlund, G.; Friberg, S. Ε. Z. Physik. Chem., 70, 39 (1970).

25.

Pople, J. Α.; Santry, D. P.; Segal, G. A. J . Chem. Phys., 43, 129 (1965).

26.

Bendiksen, B.; Friberg, S. E.; Plummer, P. J . Colloid Interface Sci., 72, 495 (1979).

27.

Bendiksen, B., Ph.D. Thesis, Chemistry Department, University of Missouri-Rolla, 1981.

28.

Schuster, P. "The Hydrogen Bond" (P. Schuster, G. Zundel and C. Sondarfy, Ed's) Vol. I, North Holland, New York, (1976) p. 120.

29.

Ekwall, P.; Mandell, L. Kolloid-Z.u.Z. Polymere, 233, 936 (1969).

30.

Clausse, M.; Sheppard, R. J.; Boned, C.; Essex, C. G. "Colloid and Interface Sci.", Vol. II (M. Kerker, Ed.) Academic Press, New York (1976) p. 233.

31.

Zulauf, M.; Eicke, H. F. J . Phys. Chem., 83, 480 (1979).

32.

Jean, Y. C.; Ache, H. F. J . Am. Chem. Soc., 100, 6320 (1978).

33.

Jean, Y. C.; Ache, H. F. J. Phys. Chem., 82, 811 (1978).

34.

Handel, E. D.; Ache, H. F. J . Chem. Phys., 71, 2083 (1979).

35.

Plummer, P. L. M. J. Glaciol., 85, 565 (1978).


1. FRIBERG AND FLAiM


36. Santry, D. P.; Crane, R. W. J. Chem. Phys., 2, 304 (1973). 37. Scott, B. F. Theor. Chim. Acta (Berlin) 38, 85 (1975). 38. Reiss, H. J. Colloid Interface Sci., 53, 61 (1975).


39. Tanford, C. "The Hydrophobic Effect", John Wiley and Sons New York (1973). RECEIVED

August 21, 1981.


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