emulsion droplet size- coexistance of nano- and micro- droplets 2

[CarlHe]

Dear All

I've encounter a problem with emulsification of an oil-in-oil emulsion. I've intended to emulsify the system to generate ca.10um droplets. but result shows that lots of 200nm droplet co-exist with 10um droplets.

Could anyone give a thought how to avoid this problem?
Thank you for your time and concern!


details:
I've been working on a DMF/Cyclohexane (4%v/v)emulsion stablized by (0.3%v/v)Span85. Inside DMF phase, PEI(polyethylenimine) is dissolved which will later be crosslinked by 2,4-TDI(toluene diisocyanate) added to the emulsion. After that, the micro-capsule will form by interfacial polyaddition reaction.
SEM is applied to evaluate the size of microcapsule and a lot of 200nm particles are observed along with 10um capsules. I believe that indicate the co-existance of nano-droplets with the 10um droplets in the emulsion. I've no idea how to avoid this problem.

attached is a SEM picture of the phenomena described above

 

[Compositepro]

The physics behind surfactant stabilized emulsions leads to a natural particle size of about 0.1 microns. To create larger particles rather than smaller ones you must limit the amount of surfactant and the amount of shear during mixing. This is difficult to get "just right". I do suggest that you read-up on emulsion science as it is somewhat complicated but essential for you to understand.
Small details, such as how you introduce one phase into the other can be very important.

 

[CarlHe]

Thank you very much for your kind reply. I do need to know more about the details of emulsion science.
I admit that it's no easy a job to get good control over droplet size via normal mixing methods, can I have some suggestions of books on this topic if there's any? Many thanks.

 

[Compositepro]

High Polymer Latices by Blackley is good but very expensive to buy new. You can get used copies on E-bay.