Macro- and Microemulsions - American Chemical Society

10 Thermal and Dielectric Behavior of Free and Interfacial Water in Water-in-Oil Microemulsions 1

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D. SENATRA , G. G. T. GUARINI , G. GABRIELLI , and M. ΖΟΡΡΙ 1

Department of Physics, University of Florence, Largo E. Fermi, 2 Arcetri, 50125 Florence, Italy Department of Chemistry, University of Florence, Via G. Capponi, 9, 50121 Florence, Italy

Downloaded by UNIV OF AUCKLAND on May 3, 2015 | http://pubs.acs.org Publication Date: March 27, 1985 | doi: 10.1021/bk-1985-0272.ch010

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The low temperature properties of a dodecane-hexanolK.oleate w/o microemulsion from 20°C to -190°C were studied vs. increasing water content (C,mass fraction) in the interval 0.024-0.4, by Differential Scanning Calorimetry and dielectric analysis (5 Hz-100 MHz). A differentiation between w/o dispersions is obtained depending on whether they possess a "free water" frac tion. Polydispersity is evidenced by means of dielec t r i c loss analysis. Hydration processes occurring, at constant surface tension, on the hydrophilic groups of the amphiphiles, at the expenses of the free water fraction of the droplets, are shown to develop "on age ing" of samples exhibiting a time dependent behavior. An energy balance between endothermic and exothermic processes of the system is presented and a model pro posed based upon the expansion of the interphase re gion by means of the formation of4-H O-moleculestruc tures on the polar groups of the surfactants. 2

It is w e l l known t h a t in r e c e n t y e a r s m i c r o e m u l s i o n s have a t t r a c t e d r e l e v a n t i n t e r e s t from b o t h t h e o r e t i c a l and p r a c t i c a l p o i n t s o f v i e w . However t h e r e is s t i l l a g r e a t d i s c u s s i o n about t h e d e f i n i t i o n o f t h e i r r e p r e s e n t a t i v e p r o p e r t i e s and even about t h e p r o p e r meaning o f t h e word " m i c r o e m u l s i o n " . Indeed such a name would i n d i c a t e a d i s p e r s e d system w h i l e m i c r o e m u l s i o n s show t h e appearence o f t r u e s o l u t i o n s , i . e . , o f homogeneous s y s t e m s . S i n c e an e s s e n t i a l r e q u i s i t e f o r t h e e x i s t e n c e o f a m i c r o e m u l s i o n is t h e p r e s e n c e o f w a t e r ( l ) , we t h i n k t h a t a s t u d y o f t h e fundamental p r o p e r t i e s o f such systems s h o u l d r e q u i r e t h e use o f e x p e r i m e n t a l approaches s p e c i f i c a l l y apt t o r e v e a l " i n p r i m i s " the behavior o f water. Moreover,besides o f course t h e h y d r o c a r b o n , b e i n g t h e o t h e r components n e c e s s a r y f o r t h e e x i s t ence o f a m i c r o e m u l s i o n a m p h i p h i l i c compounds a c t i n g as s u r f a c e a c t i v e a g e n t s , a l s o t e c h n i q u e s s u i t a b l e f o r t h e s t u d y o f systems w i t h a high s u r f a c e - t o - v o l u m e r a t i o , are requested. :

0097-6156/85/0272-0133$06.00/0 © 1985 American Chemical Society

In Macro- and Microemulsions; Shah, D.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.


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M A C R O - A N D MICROEMULSIONS

The aim o f t h e p r e s e n t work is t w o f o l d : t o r e a c h a deeper k n o w l edge o f t h e r o l e o f w a t e r in d e t e r m i n i n g t h e p r o p e r t i e s o f m i c r o e m u l s i o n s and t o i d e n t i f y t o t h e g r e a t e s t p o s s i b l e e x t e n t , t h e c o n d i t i o n o f o r g a n i z a t i o n and s t a b i l i t y o f t h e i n t e r p h a s a l r e g i o n . Low f r e q u e n c y d i e l e c t r i c a n a l y s i s in p a r a l l e l w i t h d i f f e r e n t i a l s c a n n i n g c a l o r i m e t r y (DSC) were u s e d t o s t u d y a w a t e r - i n - d o d e c a n e m i c r o e m u l s i o n by o n l y c h a n g i n g i t s water c o n t e n t , w i t h o u t m o d i f y i n g t h e i n i t i a l p r o p o r t i o n s o f t h e o t h e r components. D i e l e c t r i c a n a l y s i s was chosen t o s t u d y : i ) t h e change o f t h e w/o m i c r o e m u l s i o n as a f u n c t i o n o f i n c r e a s i n g w a t e r c o n t e n t by c o n s i d e r i n g "water" b o t h a component and a h i g h l y s p e c i f i c d i e l e c t r i c p r o b e , b e c a u s e o f t h e l a r g e d i f f e r e n c e between ε - w a t e r ( 8 0 . 3 7 ) and ε - dodecane (2.011+) at 20°C.; (2) i i ) t h e m o d i f i c a t i o n o f t h e s y s t e m ^ p r o p e r t i e s upon s o l i d i f i c a t i o n , at s e v e r a l d i f f e r e n t c o n c e n t r a t i o n s (3.); i i i ) t h e f r e q u e n c y dependence o f t h e d i e l e c t r i c l o s s o f l i q u i d samples in o r d e r t o use i n t e r f a c i a l p o l a r i z a t i o n phenomena ( M a x w e l l Wagner a b s o r p t i o n ) (U-5) t o o b t a i n i n f o r m a t i o n about t h e degree o f d i s p e r s i t y o f the system a n d , c o n s e q u e n t l y , of the e x t e n s i o n o f the interface. Thermal a n a l y s i s was employed t o a c q u i r e : i ) g e n e r a l thermodynamic i n f o r m a t i o n about a multicomponent s y s tem; i i ) s e m i q u a n t i t a t i v e e v a l u a t i o n o f the heats a s s o c i a t e d w i t h ex p e r i m e n t a l l y i d e n t i f i e d t r a n s i t i o n s with p a r t i c u l a r regard to those o f w a t e r . T h i s is t h o u g h t p o s s i b l e b e c a u s e o f t h e s m a l l and d e f i n e d w a t e r c o n t e n t o f w/o m i c r o e m u l s i o n s ; i i i ) a d e s c r i p t i o n o f t h e p r e s e n t system b a s e d on p r o p e r t i e s w h i c h do not depend on whether t h e s t r u c t u r e is known ( 5 - 6 ) . B o t h e x p e r i m e n t a l approaches are supposed s u i t a b l e t o : a) charac^ t e r i z e t h e m i c r o e m u l s i o n in t h e two d i f f e r e n t s t a t e s : l i q u i d and s o l i d ; b) i d e n t i f y t h e p r e s e n c e o f a " f r e e w a t e r " f r a c t i o n in m i c r o e m u l s i o n systems and t h e c o n c e n t r a t i o n at which t h e l a t t e r becomes d e t e c t a b l e ; c) d i s t i n g u i s h between d i f f e r e n t t y p e s o f w/o d i s p e r s i o n s d e p e n d i n g on whether t h e y p o s s e s s a f r e e water c o n t e n t . Materials

and Methods

Microemulsions. Components o f t h e i n i t i a l m i x t u r e o f t h e a c t u a l s y s tem a r e : d o d e c a n e , n - h e x a n o l and p o t a s s i u m o l e a t e whose % w e i g h t s a r e , r e s p e c t i v e l y , 5 8 . 6 ? , 2 5 . 6 ? and 1 5 . 8 ? (7^8) w i t h K - o l e a t e / d o d e c a n e = O . U ( g / m l ) and h e x a n o l / d o d e c a n e = O . 2 ( m l / m l ) . In o r d e r t o s o l u b i l i z e t h e K - o l e a t e , 2 . i + ? o f water by weight was added t o t h e former m i x t u r e which was t h e r e f o r e kept at 2 0 ° C . , s e a l e d i n t o a q u a r t z b o t t l e , f o r a pe r i o d o f one y e a r w i t h o u t u s i n g it ( 5-6) ( 9 . ) . W a t e r - i n - o i l m i c r o e m u l s i o n samples were p r o d u c e d a t 2 0 ° C . , by a d d i n g t o t h e above m i x t u r e v e r y s m a l l amounts o f double d i s t i l l e d water from a S u p e r - Q - M i l l i p o r e System w i t h a O.2 ym M i l l i S t a c k f i l t e r . I n o r d e r t o speed up t h e f o r m a t i o n o f i s o t r o p i c l i q u i d s p e c i m e n s , t h e samples were g e n t l y s t i r r e d f o r about 15 m i n u t e s . P a r t i c u l a r c a r e was d e v o t e d t o p r e s e r v e t h e in t e g r i t y o f t h e samples by m a i n t a i n i n g them s e a l e d i n t o n e u t r a l g l a s s c o n t a i n e r s at a c o n s t a n t t e m p e r a t u r e o f 2 0 ° C . The sample w a t e r con t e n t was e x p r e s s e d by t h e mass f r a c t i o n C = w a t e r / ( w a t e r + o i l ) . The c o n c e n t r a t i o n i n t e r v a l i n v e s t i g a t e d e s t e n d s from O.021+ t o O.k. The c o r r e s p o n d i n g range w i t h C in volume f r a c t i o n , is O.019 ) ( 5 - 6 ) (9.) we r e p o r t e d t h a t permanently p o l a r i z e d m i c r o e m u l s i o n specimens can be p r o d u c e d by r a p i d f r e e z i n g i s o t r o p i c l i q u i d s a m p l e s , p o l e d at 2 0 ° C . , w i t h a low l e v e l e l e c t r i c f i e l d . Moreover it was shown t h a t t h e s e samples behave l i k e p y r o e l e c t r i c b o d i e s w i t h t h e p o l a r a x i s in t h e d i r e c t i o n o f t h e f i e l d . Such a b e h a v i o r i m p l i e s t h a t , under t h e a c t i o n o f t h e f i e l d , a p a r t from é l e c t r o s t r i c t i o n phenomena t h a t a f f e c t t h e l i q u i d system as a w h o l e , t h e d i s p e r s e d phase undergoes a d e f o r m a t i o n t h a t can be e i t h e r a r e a l shape c h a n g e , as in coacervate d r o p s , o r a " g e n e r a l i z e d " d e f o r mation due t o a m i g r a t i o n o f charges o v e r m i c r o s c o p i c d i s t a n c e s , as in e l e c t r e t s . The i n t r o d u c t i o n o f a s o r t o f "shape p o l a r i t y " t o e x p l a i n t h e mechanism o f p o l a r i z a t i o n o f n o n - r i g i d s p h e r i c a l d r o p l e t s d i s p e r s e d in a c o n t i n u o u s medium, is however c o n s i s t e n t w i t h t h e f r e q u e n c y dependence o f t h e d i e l e c t r i c l o s s p l o t t e d in F i g u r e 2. In f a c t , by i n t r o d u c i n g a "shape f a c t o r " t h a t a c c o u n t s f o r t h e degree o f e l o n g a t i o n o f the d r o p l e t , a c c o r d i n g to S i l l a r s ' theory o f i n t e r f a c i a l p o l a r i z a t i o n (25) ( 5 - 6 ) , it f o l l o w s : i) t h e l o s s p r o d u c e d by a d i s p e r s i o n o f s p h e r i c a l l y shaped d r o p l e t s is much l e s s t h a n t h a t c a u s e d by t h e same amount o f m a t e r i a l d i s t r i b u t e d in t h e form o f e l o n g a t e d s p h e r o i d s ; ii) t h e d i e l e c t r i c l o s s w i l l s h i f t i t s maximum t o a l o w e r f r e q u e n c y upon a shape change o f t h e d i s p e r s e d phase toward a more e l o n g a t ed c o n f i g u r a t i o n . As a c o n s e q u e n c e , a system c o n t a i n i n g p a r t i c l e s o f d i f f e r e n t shape w i l l e x h i b i t a sequence o f l o s s maxima, c e n t e r e d at f r e q u e n c i e s l o w e r t h a n t h a t at which o c c u r s t h e maximum l o s s f o r s p h e r e s . T h e r e f o r e , in t h e c a s e o f d r o p l e t s d i f f e r i n g in s i z e - u n d e r t h e assumption t h a t l a r g e r d r o p l e t s w i l l deformate more t h a n t h e s m a l l e r onest h e d i e l e c t r i c l o s s a n a l y s i s may h e l p in d i s t i n g u i s h i n g among t h e l o s s e s c a u s e d by t h e d i f f e r e n t s i z e - d i s t r i b u t i o n s o f t h e d r o p l e t s . The b e h a v i o r o f B £ v s . f r e q u e n c y p l o t t e d in F i g u r e 2 s u g g e s t s t h a t in t h e i n t e r v a l s (O.222< C< O.31) and ( O . 3 K C < O . U ) , t h e samples are p o l y d i s p e r s e d and t h a t two t y p e s o f p o l y d i s p e r s i t y d e v e l op upon water a d d i t i o n which are d i s t i n g u i s h e d by t h e l o s s c u r v e s 2-SPS and 3 - D P S , r e s p e c t i v e l y . A c c o r d i n g t o S i l l a r s ' t h e o r y , t h e aged samples showing t h e b e h a v i o r o f curve ^ ~ F , s h o u l d c o n s i s t o f a homogeneous d i s t r i b u t i o n o f s m a l l s p h e r i c a l d r o p l e t s l i k e t h e one o b t a i n e d in t h e i n t e r v a l ( O . 0 2 U £ C £ O . 2 2 2 ) , upon m i n i m a l a d d i t i o n o f water ( c u r v e 1 - F ) . D e s p i t e t h e i n c r e a s e d sample water c o n t e n t , t h e e x p e r i m e n t a l e v i d e n c e s u p p o r t s a g a i n an i n t e r p r e t a t i o n in terms o f s p h e r i c a l - u n d e f o r m e d d r o p l e t s , w h i c h h o w e v e r , b e i n g l a r g e r , need t o be more r i g i d t o account f o r t h e o b s e r v e d t r e n d . ( 5 - 6 ) . Such a c o n d i t i o n is a c h i e v e d by t h e M

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f o r m a t i o n o f t h e U-H2O- m o l e c u l e s t r u c t u r e s accompanied by an e n t r o p y d e c r e a s e and by t h e d i s a p p e a r a n c e o f t h e f r e e water ( Δ Η ^ 0 ) . The above e n t r o p y d e c r e a s e is due t o t h e d i m i n u t i o n o f t h e freedom o f t h e water m o l e c u l e s and p o s s i b l y a l s o t o t h e f a c t t h a t , b e i n g t h e f o r m a t i o n o f h y d r a t e d s t r u c t u r e s e n t h a l p i c a l l y f a v o u r e d , such event may take place a l s o with a r e l a t i v e entropy decrease. ν

Discussion Two d i f f e r e n t t y p e s o f w/o d i s p e r s i o n s were found t o d e v e l o p in t h e i n t e r v a l s (O.02k< C< O.222) and (O.222< C< O.k). The f o r m e r , is d i s t i n g u i s h e d by ( A H = 0 ) and r a t h e r h i g h v a l u e s o f t h e R r a t i o ( = 3 - 5 ) . The l a t t e r is c h a r a c t e r i z e d b y t h e p r e s e n c e o f a f r e e water f r a c t i o n as a w e l l d e t e c t a b l e component o f t h e system ( Δ ί ^ ^ Ο ) , w i t h R r a n g i n g around a v a l u e o f 2. (See T a b l e II) In t h e " t r a n s i t i o n " r e g i o n (O.222< C< O.31) where a Δ Η ^ Ο c o n t r i b u t i o n s t a r t s b e i n g d e t e c t a b l e w i t h Δ Η - Δ Η ^ and Δ Η ^ ~ Δ Η £ , (see T a b l e I and F i g u r e 5 ) a c o n c e n t r a t i o n was f o u n d at which R- 1 ( T a b l e II). T h i s r e s u l t s u g g e s t s t h a t at t h e c o n c e n t r a t i o n 0=O.293 t h e i n t e r phase r e g i o n has r e a c h e d t h e p r o p e r e x t e n s i o n t o a l l o w t h e f o r m a t i o n o f d r o p l e t s c o n s i s t i n g o f a c o n t i n u o u s monolayer o f s u r f a c t a n t s w i t h l - H 2 0 - m o l e c u l e per h y d r o p h i l i c group, anchored t o a s h e l l o f i n t e r f a c i a l water ( m e l t i n g at - 1 0 ° C ) , t h a t e n c l o s e s an i n n e r c o r e c o n t a i n i n g a f r e e water f r a c t i o n . The d i f f e r e n c e between t h e t o t a l sample water c o n t e n t and t h e measured Δ Η c o n f i r m s in f a c t t h a t t h e r e is a p o r t i o n o f water which is n e i t h e r " f r e e " n o r " i n t e r f a c i a l " . The p r o p e r t i e s t h a t c h a r a c t e r i z e t h e w/o d i s p e r s i o n s r e c o g n i z e d in t h e above c o n c e n t r a t i o n i n t e r v a l s a r e in good agreement w i t h t h e d e f i n i t i o n u s u a l l y adopted t o d i s t i n g u i s h m i c e l l a r s o l u t i o n s from w/o m i c r o e m u l s i o n s ( 2 6 - 3 0 ) . However,by f o l l o w i n g t h e e v o l u t i o n o f t h e system a g a i n s t water a d d i t i o n , it appears t h a t a c o n t i n u o u s change o c c u r s in t h e s t r u c t u r a l c o n f i g u r a t i o n o f t h e d i s p e r s e d phase which mostly concerns the i n t e r p h a s a l r e g i o n . The c o n c l u s i o n s drawn on t h e b a s i s o f t h e d i e l e c t r i c l o s s a n a l y s i s o f l i q u i d samples, support the i n t e r p r e t a t i o n t h a t a very g r a d u a l confluence o f the d i f f e r e n t types o f d i s p e r s i o n s takes p l a c e . S u c h an i n t e r p r e t a t i o n c o u l d e x p l a i n t h e i n s t a u r a t i o n o f p o l y d i s p e r s e d samples in terms o f t h e c o e x i s t e n c e , at e q u i l i b r i u m , f i r s t , o f m i c e l l a r a g g r e g a t e s w i t h w/o m i c r o e m u l s i o n d r o p l e t s a n d , s u c c e s s i v e l y , o f a m i c r o e m u l s i o n w i t h l - ^ O - p e r h y d r o p h i l i c group m o n o l a y e r , in e q u i l i b r i u m w i t h a h y d r a t e d t y p e o f m i c r o e m u l s i o n (U-water m o l e c u l e p e r p o l a r head o f t h e s u r f a c t a n t h y d r o p h i l i c groups m o n o l a y e r ) . The l a t t e r i n t e r p r e t a t i o n is in a c c o r d a n c e w i t h S t e i n b a c h and Sucker f i n d i n g s t h a t t h e two t y p e s o f s t r u c t u r e s ( I-H2O and *+-H 0 m o l e c u l e ) , may c o e x i s t at e q u i l i b r i u m ( 2 3 ) . As shown in F i g u r e 5 by t h e two dashed v e r t i c a l l i n e s , t h e c o n c e n t r a t i o n s C=O.2T0 and 0=O.353, at which t i m e dependent phenomena were o b s e r v e d , may be r e g a r d e d as t h e upper l i m i t s o f t h e two t y p e s o f p o l y d i s p e r s e d s a m p l e s . Beyond 0=O.353 t h e o n s e t o f t h e b i c o u n t i n uous s t r u c t u r e is thought t o d e v e l o p even i f m a c r o s c o p i e a l l y , t h e samples appear i s o t r o p i c and homogeneous b e s i d e s b e i n g stable.


w

ν

5

ν

2

Conclusion From t h e ensemble o f t h e r e s u l t s some f i n a l c o n s i d e r a t i o n s :

collected

it

is

possible to


draw

10.

SENATRA ET AL.

1)

2)

3)

Thermal and Dielectric Behavior of H2O

147

r e a l l y complementary and c o n v e r g i n g i n f o r m a t i o n was o b t a i n e d by p a r a l l e l s t u d y o f c a l o r i m e t r i c ans d i e l e c t r i c p r o p e r t i e s o f t h e w/o m i c r o e m u l s i o n ; in p a r t i c u l a r , a c c o r d i n g t o o u r w o r k i n g h y p o t h e s i s , deeper knowledge o f t h e r o l e o f b o t h water and i n t e r p h a s e has been g a i n e d and it was t h u s p o s s i b l e t o e v i d e n c e t h e e x i s t ence o f two t y p e s o f water ( " f r e e " and " i n t e r f a c i a l " ) due t o t h e p r e s e n c e o f i n t e r p h a s a l s t r u c t u r e s c h a r a c t e r i z e d by d i f f e r e n t s u r f a c e water c o m p l e x e s ; t h e above l e a d s t o t h e p o s s i b i l i t y o f d i s t i n g u i s h i n g among some main t y p e s o f d i s p e r s i o n which can be t r a c e d t o , s a y , m i c e l l e s , m i c r o e m u l s i o n s and b i c o n t i n u o u s s t r u c t u r e s ; the observed c o n t i n u i t y o f behavior o f the system's c a l o r i m e t r i c p r o p e r t i e s , a p a r t from Δ Η , can be a c c o u n t e d f o r by t h e p r e s e n c e o f an e q u i l i b r i u m between any two c o n t i g u o u s s t r u c t u r e s d e v e l o p e d upon water a d d i t i o n ; t h e r e v e r s i b i l i t y o f t h e DSC e x p e r i m e n t s and t h e agreement b e tween h i g h and low t e m p e r a t u r e d i e l e c t r i c measurements i n d i c a t e t h a t t h e m i c r o e m u l s i o n f r e e z e s u n a l t e r e d j u s t l i k e a tempered multicomponent s y s t e m .


ν

k)

Acknowle dgment s F i n a n t i a l s u p p o r t o f t h i s work by t h e " M i n i s t e r o d e l l a P u b b l i c a I s t r u z i o n z " (MPI) and t h e "Gruppo N a z i o n a l e d i S t r u t t u r a d e l l a M a t e r i a " (GNSM) o f t h e C . N . R . , is g r a t e f u l l y acknowledged. The a u t h o r s e x p r e s s t h e i r g r a t i t u d e t o Mr. P a o l o P a r r i o f t h e C h e m i s t r y Department f o r h i s k i n d a s s i s t a n c e in t h e p r e p a r a t i o n o f the drawings.

Literature Cited 1.

Prince, L. M. "Microemulsions Theory and Practice"; L.M. Prince Ed.; Academic Press:New York, 1977; Chap. 1-3. 2. "Tables of Dielectric Constants of Pure Liquids", N.B.S. Circu lar 514, U.S. Department of Commerce, 1951. 3. Senatra, D. and Gambi, C. M.C.,in"SurfactantsinSolutions" K. Mittal Ed.; Plenum: New York, Vol.3, 1983, p. 1709. 4. Davies, M. In "Dielectric Properties and Molecular Behavior"; N. E. H i l l et a l . Ed.; Van Nostrand Reinhold: London,1969,Chap. 5. 5. Senatra, D., Guarini, G.G.T., Gabrielli, G. and Zoppi, M. In " Physics of Amphiphiles. Micelles,Vesicles and Microemulsions"; V. De Giorgio and M. Corti Eds.;Italian PhysicalSoc.,Int. School of Physics "E. Fermi",Course 90th, North Holland:Amster dam, 1984, in press. 6. Senatra, D., Guarini, G.G.T., Gabrielli, G. and Zoppi, M. J. de Physique, 1984, in press. 7. Shah, D. O., Science, 1971, 171, 483. 8. Prince, L. Μ., J. Colloid Interface Sci., 1975, 52, 182. 9. Senatra,D., Gambi, C.M.C. and Neri, A.P., J. Colloid Interface Sci., 1981, 79, 443. 10. Ballarò, S., Mallamace, F., Wanderlingh, F., Senatra, D. and Giu bilaro, G., J. Phys.C.,1979, 12, 4729. 11. Senatra, D. and Giubilaro, G., J.Colloid Interface Sci., 1978, 67, 448.


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Senatra, D. and Giubilaro, G., J.Colloid Interface Sci., 1978, 67, 457. 13. Senatra, D., J. of Electrostatics, 1982, 12, 383. 14. Senatra, D., Il Nuovo Cimento B, 1981, 64, 151. 15. Ballarò, S., Mallamace, F. and Wanderlingh, F., Phys. Lett. 1979 70A, 497. 16. Mallamace, F., Migliardo, P., Vasi, C. and Wanderlingh, F., Phys. Chem. Liq., 198l, 2, 47. 17. Ballarò, S., Mallamace, F. and Wanderlingh, F., Phys. Lett. 1983, 77A, 2, 3, 198. 18. Coster, W. C., Magat, Μ., Schneider, W. C. and Smith, C. P., Trans. Faraday Soc, 1946, 42A, 213. 19. Wendlandt, W. W. in "Thermal Methods of Analysis", J. Wiley and Sons: New York, 2nd Edition, 1974, Chap. 5. 20. Landolt-Boernstein in "Zahlenwerte und Funktionen", 1961, 6, II Band, 4 Teil, Springer Verlag: Berlin. 21. Handbook of Chemistry and Physics, C. D. Hogman, R. C. Weast, and S.M. Selby, Edrs.,Chemical Rubber Publish.: Cleveland, Ohio, 1959. 22. Van Turnhaut, J., In "Electrets", G. M. Sessler Ed.;Topics i n Applied Physics, Vol. 33, Springer-Verlag: Berlin, New York, 1980, Chap. 3. 23. Steinbach, H. and Sucker, Chr., Advances in Colloid Interface Sci., 1980, 14, 43. 24. Bassetti, V., Burlamacchi, L. and Martini, G., J. Am. Chem. Soc. 1979, 101, 5471. 25. Sillars, R. W., J. Instr. Engrs.: (London), 1937, 80, 378. 26. Sjöblom, E. and Friberg, S., J. Colloid Interface Sci., 1978,67, 16. 27. Friberg, S. and Burasczanska, I., Progr. Colloid and Polymer. Sci., 1978, 63, 1. 28. Jouffroy, J., Levinson, P. and de Gennes, P. G., J.de Physique, 1982, 43, 124. 29. Zulauf, M. and Eicke, H. F., J. Phys. Chem., 1978, 83, 480. 30. Robb, I. D., In " Microemulsions ", Plenum: New York, 1982. Downloaded by UNIV OF AUCKLAND on May 3, 2015 | http://pubs.acs.org Publication Date: March 27, 1985 | doi: 10.1021/bk-1985-0272.ch010

12.

R E C E I V E D June 8, 1984


Macro- and Microemulsions - American Chemical Society

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