Yes I expect so, but it wouldn't be a very good stabiliser, better to use sodium dodecylbenzene sulfonate or Aerosil AOT, 

To form water in oil emulsions its generally best to use an oil soluble surfactant rather than a water soluble one.

In the paper you refer to I suspect the PVA is helping stabilise the emulsion as well. Even so I would expect one of the other sufactants I mention above to be better and easier!

Paul

Dear Prof. Luckham,

Thank you for your answer.

You're right. Neither PVA nor SLS can stabilize W/O emulsions. As you mentioned, oil soluble surfactants are the best choices.

Yes, I also think that the PVA plays an important role in emulsification, more as viscosifier in a first step.

You have to consider that w/o emulsions always form first when dosing the aqueous phase into the oil in increments until it reverses to o/w. Critical phase ratio depends not only on emulsifier but also on speed of addition, stirrer speed and material. The viscosifier should play an important role also here. Likely, they choose this surfactant purposely to avoid formation of too small droplets or only just because it seems to be the most popular surfactant in physical chemical labs. Another important point is, they did not optimized the emulsion system to have long term storage stability. It is only an intermediate step.

Stoyan,

this is simply not true, only in terms, preferentially stabilizes an emulsion with the continuous phase where it is soluble. How well it stabilizes the emulsion is another question. Otherwise you say Prof. Peppas is lying or did not made his observations well. Only in a w/o emulsion he should be able to prepare the PVA particles.

For W/O emulsion, it will be suitable tu use a surfactant having appropriate value of the so called hydrophilic-lipophilic balance (HLB). THe HLB of a surfactant is a measure of the degree to which it is hydrophilic or lipophilic, it is determined by calculating values for the different regions of the molecule, as described by Griffin in 1949 and 1954. Other methods have been suggested, notably in 1957 by Davies. Please see the refrences below:

1. Griffin, William C. (1949), "Classification of Surface-Active Agents by 'HLB'", Journal of the Society of Cosmetic Chemists 1 (5): 311-26

2. Griffin, William C. (1954), "Calculation of HLB Values of Non-Ionic Surfactants", Journal of the Society of Cosmetic Chemists 5 (4): 249-56

3. Davies JT (1957), "A quantitative kinetic theory of emulsion type, I. Physical chemistry of the emulsifying agent", Gas/Liquid and Liquid/Liquid Interface (Proceedings of the International Congress of Surface Activity): 426–38.

Best regards

Dr Amane Jada

SDS likely complex with PVA, also there maybe a mixed film PVA/SDS stabilizing the droplets. They will have their reason to use SDS in addition to PVA. One should be a reduction of interfacial tension to ease droplet break-up.

The HLB value of SLS is 40. So, it is more appropriate to be used in oil/water emulsions. Anyway, an emulsifier with HLB value between 10-18 is better for o/w emulsions because of its active surface.  For w/o emulsions is better to use emulsifier with HLB value between 3-6, like glyceryl monostearate, span® 80, span® 60.

Emulsifier with HLB value of 4-6 are more suitable for stabilizing water in oil emulsions. As Bruna 

Dear Prof. Karakashev, I attached the article.

Neither SDS nor PVA can stabilize such an emulsion!

I've worked on this emulsion with the same recipe. Catastrophic coagulation was my result  !!!! To the best of my knowledge, there is no interaction between SDS, an anionic emulsifier, and PVA, a non-ionic polymer with so many hydroxyl and a few acetate groups, so that they form complex with each other. If you have any reference, mentioning that would be greatly appreciated. Moreover, PVA is not soluble in the continuous phase (corn oil) at all, even if it is 1 % hydrolyzed !!! Lets accept that there are so many articles, some of them published in high ranked journals, having so many mistakes :) And lets not justify those mistakes.

With all due respect. Thanks a lot for your time

Bancroft's rule states that the external phase will be the one in which the emulsifier is more soluble. Since SLS is more soluble in water than the oil, water is the continuous phase while the oil is the internal phase. In addition, SLS has a very high HLB value of 40 meaning it is water soluble and it prefers to form o/w emulsions. However, at high salt concentration, the charges on SLS are shielded and this lowers its solubility in water and may change the curvature of the interface to form w/o. Did the author mention any influence of salt concentration on the emulsion and what was the oil volume fraction? 

As stated, adding water into oil or vice versa will always first form w/o and o/w, respectively. Depending on stability, mostly by catastrophic phase inversion, further addition will lead to formation of the opposite type. One factor is here ratio of water to oil.

There are several papers in literature dealing with PVA-SDS interaction in water. Easy to locate. One example:

http://revroum.lew.ro/wp-content/uploads/2009/RRCh_7_2009/art_9.pdf

One should be very careful stating

'published in high ranked journals, having so many mistakes.' in connection with one particular article.

First of all the approach via 'cross linking' via freeze-thaw cycling is a very interesting one.

Regarding the experimental details there seem to be indeed a mistake.

'20.0 ml of a 15% aqueous PVA solution / 50.0 ml of corn oil' - 40 % volume of water in oil would be huge in a very metastable system.

Later 'PVA/SLS: oil ratio of 1: 10', i.e. 10 %.

One has to note that in this special system several details may have an influence making it hard to reproduce the results.

'dropwise' - drop size?. Material of stirrer and container? (Hydrophobic would favour w/o). 400 rpm may mean different shear situation depending on stirrer and container geometry.

Quality of polymer solution, aging etc. might have a major impact.

I assume droplet size is rather large. In this respect quality of SDS regarding hydrolysis, i.e. content of dodecanol may have a marked effect (favour w/o). There may be further aspects.

No. SLS being a hydrophillic surfactant with high HLB number, it cant be used as a an emulsifier for W/O type of emulsion, nor does it make sense to try that. However it is an excellent emulsifier for O/W emulsion, water being the external continuous phase

How can i make water soluble emulsion of Nitrobenzene