[mobbt]

i´m doing research on polystyrene spheres as template material to synthesize particles. i´m doing so in aqueous solution. but how do i prevent the polystyrene spheres from drifting to the top since they can´t interact fully?

[Enthalpy]

Hi Mobbt, welcome here!

Could you explain why the polystyrene spheres are supposed to drift upwards? Are they hollow maybe, or foam? Or the aqueous solution dense ? An other effect?

The density alone (1.05) would let polystyrene sink in water.

[mobbt]

They´re Styrofoam pellets, so they´re mostly air. i´m doing research for my master thesis and a co worker suggested them as template material, as he said they´re kind of standard as template material. i´ve read some papers where polystyrene was used as template material, but they didnt go into detail.

[Arkcon]

Unless you want a hollow template as a scaffold for some sort of hollow, or porous nano-material, then you'll have to find solid polystyrene, or maybe synthesize the beads yourself.  Or maybe suspend in a fluid much less dense than water.

[mobbt]

It is for porous nanomaterial. Later on I want to pyrolyse the organic

[Enthalpy]

I can't think of a reasonable liquid (liquid hydrogen...) as little dense as styrofoam. Possible directions:
- Have beads so small that they take long to raise; but this looks like D<1µm.
- Have a very strong current that draws the beads with it, but at D~1mm it must be very difficult. Suspending in a gas would be easier.
- Hold them with a grid. Shake the grid so its shadow changes its place often at the beads' surface.

[ATMyller]

How about using a vacuum chamber to remove the air from styrofoam. If do it on a water filled beaker the styrofoam will suck some water inside the vacuumed cavities when you release the pressure back in, creating a sort of polystyrene sponge, that will sink nicely in aqueous solutions.

[mobbt]

@ATMyller that´s a very nice idea. thanks a lot.

i also thought about snythesizing my own polystyrene spheres. i would buy styrene and add it to water and add potassium persulfate as a initiator and heat the mixture to about 70 ° C. would they be stable in alkaline solutions?

[Arkcon]

Synthesis of polystyrene beads is a basic sort of organic chemistry experiment.  You'll have to search online.  Basically, an aqueous suspension of sytrene and divinyl benzene crosslinker is mixed with an initiator I can't recall and benzyl peroxide is used as a free radical initiator.  Kept stirred gently, fairly uniform solid beads will form.

If you want to use porous commercial beads, maybe thorough mechanical stirring while building your nanoparticles  is all you need.

[Enthalpy]

The polystyrene foam I've seen up to now has closed cells and is air- and watertight in a first approximation. Is there any other?

Many open-cell foams exist as well, among them polyurethanes are common.

But first, what exactly is needed: a foam? The dense material?

[mobbt]

the dense material is needed. i tried the vacuum but the styrofoam we have seems to be closed-cell