I have developed a new organosilane molecule and I am trying to make uniform spherical organosilica particles out of it through a Stöber synthesis. I have tried a lot of compositions now and all of them gel instead of forming micron sized spheres. The organosilane I use is depicted below and is very apolar, it does not mix with water at all.
Any ideas?
Just ideas as you want
1. Prepare your molecule with SiOCH3 groups instead of SiOC3H7
2. Increase the amount of organic solvent (propyl alcohol, as I remember) in Strober system
3. May be try to dilute your molecule by TEOS, it will form spheres and takes your silane with it. I don't know is it Ok, because you have not specified the purpose
I agree that diluting this silane with TEOS is a good idea. Also, to prevent gelation, you'll certainly need to dilute the monomer, and a small alcohol is a good suggestion (thanks, S. Alekseev, for both ideas).
Regarding micron-sized spheres, the following reference provides a very robust synthesis of particles that are about 3 micrometers in diameter, with very low size dispersity:
DOI: 10.1039/b003221m
J. Mater. Chem., 2000, 10, 2289-2293.
I have changed only one thing to improve the yield - allow the solution to sit for about an hour, rather than only 10 minutes.
In your case, you could use a combination of TEOS and your silane. Alternatively, could you start the particles with TEOS, then add your monomer sequentially?
Thank you for these answers already.
Diluting with TEOS I cannot do because the purpose is to make a hydrolytically stable organosilica material. However I could indeed start out with TEOS and then grow the particles with the organosilane.
The methoxy variant is also a good idea, but then I have to ask is it possible to switch out the ethoxy groups for methoxy groups post synthesis?
That article also looks interesting, that is not really a Stöber synthesis right? I see it is basically water, TEOS and acetic acid. I am certainly going to try this out.
Thank you for the answers so far, but please do not hesitated to continue on the subject.
The guys have given very good suggestions. Here I like suggest
(1) use very low concentration (1 - 2%)
(2) use alkaline catalyst ( Me4NOH, for example)
(3) add some surfactant as an allternative
(4) well control of stirring speed.
(5) increase temperature because your monomer is hard to hydrolyse.
Read these papers. They might give you some newer ideas.
I. Halasz et al., Phys. Chem. C 2011, 115, 24788–24799
R. Zaleski et al., RSC Advances 2012, , 2, 3729-3734.
Yi, J. Wong et al., J. Am. Chem. Soc. 2011, 133, 11422-11425.
hi,
Make methanolic solution of cationic surfactant, then add your silica precursor followed by the addition of NaOH. Do the ageing process under autoclave condition.
(for removing surfactant, u can go for solvent extaction method)
Since you want solid, non-porous particles, you probably don't want to use surfactant. A small amount might be ok, but only enough to solubilize your monomer. If it's anywhere near the critical micelle concentration, you'd probably generate porosity in your silica.
You can use the procedure showed in this paper Chem. Mater. 2003, 15, 4247-4256.
At the end you will obtain spherical silica with the only TEOS silica precursor.
If you add any silane to TEOS, you will modify the shape of the particles.
In addition you can see my paper RSC Adv., 2013,3, 5832-5844
http://pubs.rsc.org/en/content/articlelanding/2013/RA/C3RA22706E there I used different ratio between TEOS and silane, and low amonth of surfactant in other to reduce the surface area/porosity and have less impurity.
Try the following reference, it may be helpful. you may have to change to the Si(OMe)3 groups however
http://pubs.acs.org/doi/abs/10.1021/cm101243m
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