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SINGLE CRYSTALS OF CUBIC TERNARY PHASES IN THE DDDAB/D2O/OCTANE SYSTEM
M. Cruz, A. Vallêra, C. Toprakcioglu
To cite this version:
M. Cruz, A. Vallêra, C. Toprakcioglu. SINGLE CRYSTALS OF CUBIC TERNARY PHASES IN
THE DDDAB/D2O/OCTANE SYSTEM. Journal de Physique Colloques, 1990, 51 (C7), pp.C7-109-
C7-114. �10.1051/jphyscol:1990710�. �jpa-00231109�
SINGLE CRYSTALS OF CUBIC TERNARY PHASES IN THE DDDAB/DZO/OCTANE SYSTEM
M.M. CRUZ, A.M. VALL%RA and C. TOPRAKCIOGLU'
Dep. de Fisica, Univ. d e Lisboa/CFMC, Campo Grande, Ed. Cl, F-1700 Lisboa, Portugal
Cavendish Lab., Univ. of Cambzidge. Madingley Road, GB-Cambridge CB3 OHE, Great-Britain
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La c o n n a i s s a n c e d e s s t r u c t u r e s c u b i q u e s q u i a p p a r a i s s e n t d a n s l e s s y s t e m e s t e r n a i r e s t e n s i o a c t i f / e a u / h u i l e p o u r r a i t d t r e b i e n p l u s p r e c i s e s i l ' o n d i s p o s a i t d e m o n o c r i s t a u x . La p o s s i b i l i t e d ' e n c r o y t r e e s t demontree d a n s c e t e t u d e . On p r g s e n t e d e s r e s u l t a t s de d i f f r a c t i o n de n e u t r o n s e t d e r a y o n s X a u x p e t i t s a n g l e s p a r les p r e m i e r s m o n o c r i s t a u x o b t e n u s pour l e s y s t e m e DDDAB/D20/octane.A b s t r a c t
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P r e c i s e knowledge of t h e c u b i c s t r u c t u r e s a p p e a r i n g i n t e r n a r y s y s t e m s s u r f a c t a n t / w a t e r / o i l can b e a c h i e v e d i f s i n g l e c r y s t a l s o f t h e s e p h a s e s c a n b e grown. I n t h i s work t h i s i s shown t o b e p o s s i b l e . Small a n g l e X-ray a n d n e u t r o n s c a t t e r i n g r e s u l t s a r e p r e s e n t e d f o r t h e f i r s t s i n g l e c r y s t a l s o f t h i s t y p e , grown f o r t h e s y s t e m DDDAB/D20/octane.Microemulsions a r e d i s p e r s i o n s o f o i l a n d w a t e r , s t a b i l i z e d by t h e p r e s e n c e of a m p h i p h i l i c m o l e c u l e s ( s u r f a c t a n t t h a t i n some c a s e s n e e d s a l s o t h e a d d i t i o n of a C O - s u r f a c t a n t ) . I n t h e s e t e r n a r y s y s t e m s o r d e r e d p h a s e s c a n b e found1r2.
Numerous i n v e s t i g a t i o n s , i n c l u d i n g s e l f - d i f f u s i o n a n d c o n d u c t i v i t y measurements3t4, showed t h a t some o f t h e o r d e r e d s t r u c t u r e s a r e c o n t i n u o u s b o t h i n t h e o i l a n d t h e w a t e r p h a s e s . I n s u c h b i c o n t i n u o u s s t r u c t u r e s , nowadays w e l l e s t a b l i s h e d , s e v e r a l w e r e f o u n d t o h a v e c u b i c ~ y r n r n e t r y ~ . ~ . A p o s s i b l e d e s c r i p t i o n o f t h e s e 3 - d i m e n s i o n a l l y o r d e r e d s y s t e m s i s b a s e d t h e n on a p e r i o d i c s u r f a c e s e p a r a t i n g a w a t e r l a b y r i n t h from a n i n t e r p e n e t r a t i n g o i l l a b y r i n t h . We c a n t h i n k o f a s i m p l e s u r f a c e
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a s s o c i a t e d w i t h a s u r f a c t a n t monolayer-
s e p a r a t i n g o i l and w a t e r domains, o r assume t h a t t h e s u r f a c e i s a s s o c i a t e d w i t h a b i l a y e r t h a t s e p a r a t e s domains o f t h e same n a t u r e . The f i r s t e x a m p l e s o f t h i s t y p e o f c u b i c s t r u c t u r e s a p p e a r e d i n b i n a r y w a t e r - l i p i d s y s t e m s and were o f t h e s e c o n d t y p e 7 ; t h e f i r s t c o n v i n c i n g e v i d e n c e f o r t h e e x i s t e n c e o f s t r u c t u r e s o f t h e monolayer t y p e was r e p o r t e d o n l y r e c e n t l y 8 .Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1990710
COLLOQUE DE PHYSIQUE
G e o m e t r i c a l l y t h e s e i n t e r f a c e s a r e t e n t a t i v e l y d e s c r i b e d by i n f i n i t e p e r i o d i c c o n s t a n t c u r v a t u r e s u r f a c e s g .
The e x p e r i m e n t a l s t u d y o f t h e s e o r d e r e d s y s t e m s i s u s u a l l y done by X-ray o r n e u t r o n s m a l l a n g l e s c a t t e r i n g from p o l y c r y s t a l l i n e s a m p l e s . However, a much more d e t a i l e d a n d p r e c i s e d e s c r i p t i o n o f t h e i r s t r u c t u r e s c a n b e hoped f o r i f s i n g l e c r y s t a l s a r e a v a i l a b l e .
I n t h e p r e s e n t work w e r e p o r t s m a l l a n g l e X-ray a n d n e u t r o n s c a t t e r i n g measurements i n t h e f i r s t s i n g l e c r y s t a l s grown f o r t h e s y s t e m DDDAB(didodecy1 d i m e t h y l ammonium bromide)/D2O/octane.
DDDAB h a s t h e i m p o r t a n t p r o p e r t y o f f o r m i n g m i c r o e m u l s i o n s w i t h o u t t h e a d d i t i o n o f a n y C O - s u r f a c t a n t . Being p r a c t i c a l l y i n s o l u b l e b o t h i n o i l and w a t e r , i t s c o n c e n t r a t i o n d e t e r m i n e s t h e o i l - w a t e r i n t e r f a c i a l a r e a . The system s t u d i e d , DDDAB/DzO/octane, a p p e a r s a s a v e r y r i g i d non b i r e f r i n g e n t g e l i n a l a r g e domain which e x t e n d s f r o m 35% t o 7 7 % w a t e r c o n t e n t , t h e c u b i c zone r e p r e s e n t e d a p p r o x i m a t e l y i n t h e p h a s e d i a g r a m o f f i g . 1 . A l l t h e p h a s e s i n t h e s e r e g i o n show t h e i n t e r e s t i n g p r o p e r t y o f " r i n g i n g " : t h e y p r o d u c e a c l e a r l y a u d i b l e sound when t a p p e d . R i g i d i t y i s h i g h e r f b r t h e p h a s e s w i t h l o w e r w a t e r c o n t e n t .
F i g . l : P a r t i a l p o s i t i o n o f t h e
D20 80 60
O c t a n e ->
p h a s e d i a g r a m f o r t h e s y s t e m DDDAB/DgO/octane c u b i c p h a s e r e g i o n s .
s h o w i n g t h e
Small a n g l e X-ray d i f f r a c t i o n p a t t e r n s f o r t h e s e s y s t e m s show s p o t t y Debye- S c h e r r e r r i n g s , i n d i c a t i n g t h e e x i s t e n c e o f l a r g e o r d e r e d domains. Based on t h e s e o b s e r v a t i o n s , we c h o s e o u r s y s t e m i n t h e low w a t e r l i m i t o f t h e c u b i c r e g i o n , c o r r e s p o n d i n g t o t h e c o m p o s i t i o n 4 8 . 3 / 3 6 . 4 / 1 5 . 3 ( p e r c e n t w e i g h t r e s p e c t i v e l y f o r DDDAB/D2O/octane). A diamond s t r u c t u r e h a s b e e n a s s i g n e d t o t h i s c o m p o s i t i o n l O .
o b t a i n e d was r e m e l t e d by h e a t i n g t o a t e m p e r a t u r e a few d e g r e e s above i t s m e l t i n g p o i n t (45OC) a n d i n t r o d u c e d t o X-ray c a p i l l a r y t u b e s of lmm d i a m e t e r . These were s e a l e d i m m e d i a t e l y a f t e r w a r d s .
S i n g l e c r y s t a l s were t h e n grown u s i n g a molten zone t e c h n i q u e , w i t h a growth v e l o c i t y of l e s s t h a n 3mm/h.
F i g . 2 : O p t i c a l m i c r o s c o p e p h o t o g r a p h s o f two s a m p l e s : ( a ) a s f i l l e d i n t o t h e c a p i l l a r y t u b e ; ( b ) s u b m i t t e d t o ' o n e growth c y c l e .
F i g . 2 shows o p t i c a l m i c r o s c o p e p h o t o g r a p h s of two s a m p l e s : one s u b m i t t e d t o no t r e a t m e n t , t h e o t h e r a f t e r one m o l t e n zone g r o w t h c y c l e . W e c a n c o n c l u d e t h a t t h e t u b e f i l l i n g i n d u c e d some p h a s e s e p a r a t i o n b u t , a f t e r o n e g r o w t h c y c l e , t h e t r e a t e d zone h a s a n homogeneous a p p e a r a n c e w i t h o u t p h a s e s e p a r a t i o n .
X-ray s c a t t e r i n g m e a s u r e m e n t s t o o k p l a c e a t t h e M.R.C. L a b o r a t o r y of M o l e c u l a r B i o l o g y , Cambridge, and n e u t r o n s c a t t e r i n g e x p e r i m e n t s i n t h e C . E . A . L a b o r a t o i r e Leon B r i l l o u i n , S a c l a y .
P
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single c r y s t a l6 p o l w s t a l
F i g . 3 : Comparison between n e u t r o n d i f f r a c t i o n p a t t e r n s o b t a i n e d f o r one s i n g l e c r y s t a l , i n t e g r a t e d i n a n g l e , and t h e p o l y c r y s t a l l i n e i n i t i a l m a t e r i a l .
COLLOQUE DE PHYSIQUE
To c h e c k f o r c o m p o s i t i o n c h a n g e s d u r i n g c r y s t a l g r o w t h , w e compared t h e n e u t r o n d i f f r a c t i o n p a t t e r n o b t a i n e d w i t h a s i n g l e c r y s t a l , i n t e g r a t e d f o r a s m a l l r e g i o n i n a n g l e , w i t h t h a t o f t h e p o l y c r y s t a l l i n e i n i t i a l m a t e r i a l ( f i g . 3 ) . T h e r e i s o n l y a s l i g h t d e v i a t i o n o f t h e p o s i t i o n of t h e f i r s t r e f l e c t i o n , i n d i c a t i n g t h a t t h e r e i s no i m p o r t a n t c o m p o s i t i o n c h a n g e .
iie show i n f i g s . 4 a n d 5 e x a m p l e s o f t h e s m a l l a n g l e X-ray s c a t t e r i n g r e s u l t s f o r r e c r y s t a l l i z e d g e l s , o b t a i n e d by r o t a t i o n of t h e samples a b o u t an
a x i s p e r p e n d i c u l a r t o t h e d i r e c t i o n o f t h e i n c i d e n t beam. By s c a n n i n g t h e c a p i l l a r y t u b e s l o n g i t u d i n a l l y , and from t h e i n v a r i a n c e o f t h e X-ray p a t t e r n , we c o u l d c o n c l u d e t h a t c r y s t a l s w i t h volumes o f t h e o r d e r o f t h r e e c u b i c m i l l i m e t e r s a r e p r e s e n t .
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-180 -120 0 -60 0 60 120 180 T h e t a (degrees)
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F i g . 4 : X-ray s m a l l a n g l e s c a t t e r i n g i n t e n s i t y f r o m o n e of t h e s a m p l e s i n t e g r a t e d f o r a c o m p l e t e r o t a t i o n a b o u t a v e r t i c a l a x i s : ( a ) 2-dimensional X- r a y d i f f r a c t i o n p a t t e r n ; ( b ) i n t e n s i t y i n t h e "Debye-Scherrer r i n g " shown i n
( a ) a s a f u n c t i o n o f i n - p l a n e a n g l e ( O0 c o r r e s p o n d s t h e d i r e c t i o n o f t h e r o t a t i o n a x i s ) .
0 100 200
-180 -120 -60 0 60 120 180 Theta (degrees)
3 0 0 7 . - ; - - - - -
200
too
(a) (b)
F i g . 5 : Same a s f i g u r e 4 f o r a n o t h e r s a m p l e . The v e r t i c a l l i n e s mark t h e p o s i t i o n o f t h e c a l c u l a t e d ( n n 0) s p o t s f o r two d i f f e r e n t s i n g l e c r y s t a l s
( d a s h e d and f u l l l i n e s ) .
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100 200The vertical lines in figs. 4b and 5b mark the positions of the (n n 0 ) planes calculated from two of the known diffraction spots: agreement with experimental results is good. As can be seen from the XY pattern in figs. 4a and 5a, no intense second order could be detected in the range of these spectra.
The experimental conditions were not ideal. These first experiments were not yet aimed at structure solving, but rather at simply testing the possibility of single crystal growth. One major drawback with the X-ray experiment was that we have no information on the sample rotation angle $ at which each of the Bragg reflections occurred (another difficulty was that long exposure to the X-ray beam progressively destroyed the crystalline structure; the reason for this is still unknown). Information on the angle I$ was already available in a similar SANS (Small Angle Neutron Scattering) experiment, but too large a beam area was used and so more than one crystal was always illuminated by the beam. Both these limitations will be overcome in future experiments.
The results presented here are not sufficient for definitive conclusions on the crystal structure. We only demonstrate that the first Bragg reflection is due to (n n 0) type planes and that no intense second order was detected in the range of the experiment, for the composition studied.
The main conclusion is that it is possible to grow macroscopic single crystals of the cubic phases appearing in the ternary system DDDAB/D20/octane.
The mosaic spread was not carefully measured but it is of the order of one degree only.
Acknowledaments
We would like to thank A.R.Faruqi from M.R.C. for making possible the X-ray experiments and the Lab. Leon Brillouin for providing neutron beam facilities.
One of us (M.M.C.) would like to thank L.Auvray from L.L.B. for help during the neutron experiments.
This work was partially funded by a NATO grant.
References
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COLLOQUE DE PHYSIQUE
/4/ M.Clausse, P.Peyerlasse, J.Hei.1, C.Bonod and B.Lagourette, Nature 293 (1981) 636
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660
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