After going through a literature survey and some experimental work, I came to know that stabilizing oil-in-oil Pickering emulsions are more challenging task than stabilizing oil-in-water or water-in-oil emulsions.
There are very few (but important) research papers published by some of the researchers around the world for stabilizing oil-in-oil Pickering emulsions by modifying surface properties of solid particles. Hope much more work may be going on in this field.
If we could develop a simple strategy (without or with surface modifications of solids) for stabilizing oil-in-oil Pickering emulsions, it will be helpful for opening doors of new research in the field of colloidal and interfacial science. This will be helpful in developing a new strategy for novel drug delivery systems for pharmaceuticals, etc.
Q. I want opinions from experts and researchers who are working in the field of colloidal and surface science that why stabilizing oil-in-oil Pickering emulsions is not an easy task and how to design strategies/experiments for stabilizing oil-in-oil Pickering emulsions.
Amid Laxman Sadgar
My simple explanation is that in a Pickering emulsion one is typically dealing with a 4-phase system as opposed to an oil-in-water emulsion where we have oil-surfactant-water (3 phases in the simplest analogy). Dispersing a fine solid to (partially or fully) cover a surface is not at all easy. Some of the difficulties are outlined in this webinar (registration needed):
Dispersion and nanotechnology
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat
I watched the webinar, indeed dispersion is a practical and economical event.
The webinar was informative and I came across many new terminologies like "Clusters synonymously used nowadays for agglomeration''
U explained nano and micro material very well, also the zeta potential portion was covered well. I also got that the net charge of particles can be calculated by AFM.
I got some ideas after watching the lecture for stabilizing oil-in-oil emulsion.
Thank you soo much for the suggestion Alan F Rawle sir.
Amid Laxman Sadgar
You want to collect oil with the help of oil. This idea is implemented by us in the patent. The iron ore concentrate enriched with iron oxides is dispersed in the oil. It turns out "magnetic fluid". Magnetic fluid is sprayed from a boat or helicopter over an oil spill in a lake and then collected by a special magnetic drum with a conveyor, which is on the boat. On the boat, a centrifuge separates the iron oxide powder and it is sent to prepare a new magnetic fluid. An article and patents on this subject are attached.
Article Chemistry for Sustainable Development 20 (2012) 315322 Iron...
Patent SKIMMING DEVICE
Patent POWDERED MAGNETIC SORBENT FOR COLLECTING PETROLEUM, OIL AND ...
As regards the preparation of an oil/oil emulsion, this is not possible. It's like trying to make a water/water emulsion. There will be dissolution. It is possible to prepare hard wall capsules of one oil in another oil. But this composition will no longer be called emulsion. If the nanoparticles are not firmly bound, such an emulsion will break down. Maybe the pharmacists call it Pickerig's emulsion. But we physical chemists are not allowed to do this.
Oil-in-water emulsion has 3 phases but oil-in-oil subjected to 4 phase system. But oil-in-oil emulsions can be stabilized using di-block carbon nanoparticles through RAFT (Reversible Addition Fragmentation Transfer) in the study (Rymaruk et al, 2020). The emulsions were classified based on mean droplet size using optical microscopy. Some of the key information are available here:Article Oil-in-Oil Pickering Emulsions Stabilized by Diblock Copolym...
Shuraik Kader
In the article you proposed, bio-sourced oil dispersed in silicone oil was prepared. There are water-soluble silicon oils and water-insoluble silicon oils. This is an example of exotic "oils".
Pickering particles nanoparticle size and core-forming block composition. This is an example of hard wall capsules of one oil in another oil. I wrote about it above.
Yuri Mirgorod thanks for the suggestion.
Yes sir, the main hurdle in stabilizing oil-in-oil Pickering emulsions is almost all pairs of oils are miscible/soluble in each other (except some). These are the pairs of oils that are immiscible in each other and utilized for stabilizing oil-in-oil emulsions such as N, N-Dimethylformamide:Hexane/Decane, Acetonitrile: Cyclohexane/Hexane, Glycerol:Decane. But this system can’t be utilized for pharmaceutical applications. Alternatively, this can be utilized in other applications.
Shuraik Kader Thanks for response.
Question or doubt: If we design a solid material in such a way that the solid will behave like a rigid barrier (but flexible) against avoiding solubilizing of oil phases. Is it possible to use such a system to stabilize oil-in-oil Pickering emulsion? Can we call such a system oil-in-oil emulsion or as you said it will be also hard wall capsules of one oil in another oil?
Amid Laxman Sadgar
Explain N,N-Dimethylformamide:Hexane/Decan emulsion in more detail. Please provide a link. There may be others that you cited as an example.
Yuri Mirgorod
sir,
It’s a DMF-Octane system, not DMF-Decane.
This is the paper in which DMF-in-Octane and Acetonitrile-in-Octane Pickering emulsion is stabilized by amino-modified graphene oxide particles. This work is a good initiative in stabilizing oil-in-oil Pickering emulsion.
Article Controlling Oil-in-Oil Pickering-Type Emulsions Using 2D Mat...
This is another report in which modified polymeric compounds were used for stabilization acetonitrile-in-octane and Dodecane-in-acetonitrile emulsion. I am not sure this is Pickering emulsion or not.
Article Synthesis of Poly(amide-thioether) with tunable hydrophilici...
Please suggest to me how we can utilize ideas from such articles to work on stabilizing oil-in-oil Pickering emulsion.
Amid Laxman Sadgar
The DMF/octane system and similar emulsions are the same as water/octane. These are heterogeneous systems. The colloidal chemistry you want to work in is exploring systems that have the properties of heterogeneity and dispersion. Octane is partially soluble in acetonitrile, but it is also slightly soluble in water. There is still heterogeneity in the system
DMF, DMS, AN toxic solvents. They are used in the process when water cannot be used or more money can be obtained.
The continuous phases described in the articles you mentioned can also be obtained in conventional emulsions by changing from water/oil to oil/water emulsions.
I have written enough about my relationship with oil/oil pickering emulsions.
Dear Yuri,
'the preparation of an oil/oil emulsion, this is not possible. It's like trying to make a water/water emulsion.' Statement seems logical at first glance, however, it is not true - nor for water/water nor for oil/oil. All what you need is to ensure that there is limited miscibility (solubility). For water/water emulsions (you easily find literature at the www) you start with aqueous 2-phase systems. There is some minor solubility also in w/o and o/w emulsions, which is the basis for Ostwald ripening.
difficulty in stabilizing oil/oil emulsions, e.g., mineral oil/silicone oil, by solids is finding/designing appropriate particles having a well balanced attraction towards both oils. This is easier, when dispersion media and dispersed phase have largely different properties as in case of oil/water. Likely, specially designed Janus particles may work.
Dear Titus Sobisch
If you are contacting me, then you need to contact me as the RG robot asks. When you contact, he does not report the letter to the addressee. I accidentally looked at your post. If there is limited solubility, then this is already a heterogeneous system, which I wrote about. However, it is not water/water and oil/oil. These are homogeneous systems. Incidentally, the water/water phase transition accompanies surfactant micellization. But this is a quantum thermal transition that I discovered.
Deleted research item The research item mentioned here has been deleted
Dear Yuri Mirgorod
to better explain - water/water systems are the like aqueous dextrane / aqueous PEO solutions, oil/oil systems like mineral oil / silicone oil or fluorinated hydrocarbons. E.g., for the first water is continuous phase and dispersed phase as well. One example Aqueous Two-Phase Systems: simple one-step process formulation and phase diagram for characterisation.
Dear Titus Sobisch
We are talking about different systems. Everyone believes that oil includes hydrocarbons, fats, oil refinery products.
You think that oligomers of siloxanes belong to the oil. Oligomers can be composed of four monomeric units. Such siloxane oligomers are partially soluble in water. Oligomers of 20 monomeric units are insoluble in water. It's not oil. It is called so by specialists who earn money in cosmetics, face plastics, women's breasts silicone. We chemists should call it the siloxane oligomer and add the molar mass. Write your system as a 350 molar mass siloxane oligomer/decane. Now I would agree that if you add solid Janus nanoparticles, you can probably get Pickering emulsions in this system.
Yuri Mirgorod,
agree, that description oil/oil is a bit short and 'oil' is not very much defined. Much better to name it more precisely mineral oil, silicon oil, vegetable oil ...
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