Die Eigenschaften von Ölemulsionen

Ellis, Ridsdale

doi:10.1515/zpch-1912-0145

Cited by 12 publications

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“…Nevertheless, the observed stability (weeks, months) is long in comparison to other additive-free oil-in-water emulsions (21,30,31). The efficient stabilization solely by self-charging contradicts the common belief that stable emulsions require emulsifiers (1,2) and is consistent with the pioneering investigations of Ellis (32). We successfully made charge-stabilized, crystal-forming water-in-oil emulsions with various solvents, but failed with some others (Table 1).…”

Section: Resultssupporting

confidence: 53%

Electrostatics at the oil–water interface, stability, and order in emulsions and colloids

Leunissen

Blaaderen

Hollingsworth³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

268

256

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Oil-water mixtures are ubiquitous in nature and are particularly important in biology and industry. Usually additives are used to prevent the liquid droplets from coalescing. Here, we show that stabilization can also be obtained from electrostatics, because of the well known remarkable properties of water. Preferential ion uptake leads to a tunable droplet charge and surprisingly stable, additive-free, water-in-oil emulsions that can crystallize. For particle-stabilized (''Pickering'') emulsions we find that even extremely hydrophobic, nonwetting particles can be strongly bound to (like-charged) oil-water interfaces because of image charge effects. These basic insights are important for emulsion production, encapsulation, and (self-)assembly, as we demonstrate by fabricating a diversity of structures in bulk, on surfaces, and in confined geometries.colloidosomes ͉ Pickering ͉ Wigner crystal ͉ self-assembly ͉ low polar T he stabilization of emulsions and colloidal particle suspensions against aggregation and phase separation is an ancient problem. Whereas ''emulsifiers,'' for example, surfactants and small particles, are commonly used to prepare stable oil-water mixtures, solid colloids often are stabilized by a charge on their surface (1-3). Charged entities are expected in high dielectric constant ( ) liquids, such as water ( Ϸ 80), where the energetic penalty for charge separation is small. Recently, however, the focus has shifted to low dielectric constant media, in which electrostatics can also play a surprisingly dominant role (4-10), producing fascinating phenomena like the extraordinary crystal in Fig. 1A. Here, poly(methylmethacrylate) (PMMA) spheres (radius a c ϭ 1.08 m) were suspended in a density matching mixture of cyclohexyl bromide (CHB) and cis-decalin (CHBdecalin; Ϸ 5.6). They form body-centered-cubic Coulomb or ''Wigner'' crystals, with lattice constants up to 40 m (5), similar to one-component plasmas (11). Importantly, in this low-polar solvent, charge dissociation still occurs spontaneously (7), contrary to truly apolar media ( ϳ 2) that require charge stabilizing surfactants (6,8). Although electrophoresis (see Materials and Methods) shows that the particles carry a significant charge, Z Ϸ ϩ450 e (where e is the elementary charge), such extremely large lattice constants are surprising. Assuming a screened Coulomb pair potential (12) † † , the particle interaction range will depend on the ion concentration, n, in the solvent through the Debye screening length, Ϫ1 ϰ n Ϫ1/2 . Wigner crystals require an extremely low ionic strength, so that the screening length is many particle diameters and the interaction almost purely Coulombic. We estimate Ϫ1 Ϸ 1.6 m only, for CHB-decalin (see Materials and Methods), but discovered that the presence of water (even minute quantities) reproducibly induces these crystals by tremendously increasing the screening length. Apparently, the immiscible water phase acts as an ''ion sink'' for the charged species in the oily solvent. These intriguing observations led ...

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Section: Resultssupporting

confidence: 53%

Electrostatics at the oil–water interface, stability, and order in emulsions and colloids

Leunissen

Blaaderen

Hollingsworth³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

268

256

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Physikalische Chemie der Lacke 14. Mitteilung

Schäfer¹

1943

Fette Seifen

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Emulsionen 1$i]d Kritnlmungs~ruck nung, namlich aus den1 Kriiniinungsdruck. Unter dcm auf die Fliicheneinheit einer OberflQche ausgeiibten Kriinimungsdruck versteht man jenen zusltzlichcn positiveil oder nqaliven Druck, ' der durcli die Kriinirnung der Oberfllche bedingt ist. Belrachtet man zu diesem Zweck ein dopyelt gekriinimtes Oberfllichenstiick (Bild l l O ) , so betrigt dcr Kriimmungsdruck, unter formalcr Beibeliallung des Begrimes der Oberflachenspannung P K~ = u [-+-I 1 1 Lgr.cm-1 sec-21 (113) rl r2 wenn rl und r2 die Kriirnmungsradien der herausgegriffenen Fliichenstreifen bedeuten. Aus den Lehren der Geometrie crgiht sich namlich, daO fur einen beliebigen Punkt irgendincr Flachc die Summe der rcziproken Werte drr Kriim-3 iungsradien in irgend zwei zueinander senkrechlen Nornialschiiitten ininier denselbcn Wert hat. Diese Summe heiBt niittlere Kriimmulg. Der Kriinimungsdruck einer Fliiche uber eine ausfiihrliclie Zusammenfassung siehe z. B. C l a y t o n , Die Theorie der Emulsionen und der w u l g i e r u n g . Verlag J. Springer, Berlin 1924. *) 13. Mitt. Felte u. Seifen 60, 356 [1943]. 1876) Wo. 0 s t w a 1 d , Kolloid-Z. 6, 103 [1910] 1u7u) 37, IQ7O) W. C. Mc L e w i s . .Kolloid-Z. 5, 913 [1909]. 1e80) siehe z. R. L. G. K 11 a 1) p , Trans. Faradny Sac. 17, lgR1) z. H. H. E 1 1 i s , Z. physik. Cheni. 80, 604 (19121. lgat) frrnrr F. P o w i s , %. physik. Chem. 89, 91 [l9lbl. loss) sirhe H. R e c h h o l d , Die Kolloide i n Hiologie iind Mcdizin, Seile 376, Verlag Th. Steinkopff, Dresden 1919. lQR4) frrner S c h II I t z und C h a n d 1 e r , J. biol. Chemistry 46, 133 [ISZll. loR5) V. H e II r i , Kolloid-Z. '1, 116 [ 19061. lgRa) sirhe 11. F r r II 11 d 1 i c 11 , Kapillarchrniic. 2. Anfl., Scilr 1.71 IT., I m . 136, Akad. Verl. Grs., Lripzig 1923. 1gR7) 11. A . G a r d n c r und C. H o 1 t , U. S . Paint Manrif. Ass. Circ. 124, 1 119211. 1oR8) I. I, a n g m n i r , J. Anier. diem. SOC. 39, 1848 [1917]. 1Q8g) siehe auch W. D. H a r k i n s, E. C. H. D a v i e s und G. L. C 1 a r k , J. Ainer. cheni. Soc. 39, 354, 541 [1917]. lQM) N. K. A d a m , Nalure 107, 522 [1921]. 735 [1901]. 457 [l922]. 400 Felte und Seifen 50. Jahrgang Molekiile gegen die diese Oherflache unigehende lQnl) Vgl. ferner 1' . W o o 6 , C. rend. 173, 387 [IWt]. ZOoO) M. 13 n u d o u i 1 1 , Melliands Tcxlilber. 17, 654, 932 *Ool)

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Elektrische Erscheinungen an Grenzflächen

Sen

1926

Z. Anorg. Allg. Chem.

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Die Eigenschaften von Ölemulsionen

Cited by 12 publications

References 0 publications

Electrostatics at the oil–water interface, stability, and order in emulsions and colloids

Electrostatics at the oil–water interface, stability, and order in emulsions and colloids

Physikalische Chemie der Lacke 14. Mitteilung

Elektrische Erscheinungen an Grenzflächen

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