I am looking for a polymer that very easily dissolves in n-hexane but is completely insoluble in acetone. I read somewhere that LDPE should work, but my experiments with an ordinary polyethylene foil and a bottle show otherwise. Why?
I searched sci groups and the Web, and I found this so far :
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There are a few different polymers on that page that are claimed to work in the way I want. Do you know if those polymers can be easily spin-coated after dissolution in hexane? I am going to prepare a thin film from the polymer I look for.
If these questions seem to be too obvious for you - please, excuse me - I am not a chemist.
Perhaps polyalphaolefins like poly(decene) will work. A good starting point to assess solubilities is to compare the (Hildebrand) solubility parameters. They can be found in different Handbooks and probably on the web.
I read somewhere that LDPE should
The molecular weight is too high.
You could also try to snythesize a polymer, e.g. an acrylate with long side-chains (stearyl). These polymers can then also incoroporate other functionalities which you might need for your application.
Those wll set you back some serious bucks. You are looking at precursors to polymer solid supports for single site Zieglar-Natta catalysts (like InSite). Those babies can give you millions of catalyst turnovers/site so a gram of catalyst gets you tonnes of product. The spports are priced accordingly, amortizing to only a small fraction of a cent/gram product. Note that there are a million grams in a tonne.
You are mostly looking at monomers.
"Polymer Handbook" Brandrup and Immergut, chapter "Solvents and Non-Solvents for Polmers." Choose what you like.
You might begin by switching your desired solvent and non-solvent (then you have natural resins like colophony, copal, and shellac and you can fart about "green chemistry") or choosing a different pair. Go for something like aromatic or chlorinated solvents vs. acetone. That will get you into polyolefins including natural rubber.
A good time to put the "inexpensive" into a product is when it is still in research. As soon an an engineer gets his claws on it you are screwed as he optimizes.
Thank you all. You've been really helpful. I think I'll try first to find a LDPE with shorter chains and try again dissolving it in hexane. As Frank Logullo wrote - it may work only above 100C, which may not be suitable for my applications. Anyway, the other option is always to visit the nearest library and check out about some handbooks (thanks for the tips!).
Hydrocarbon resins (e.g from Hercules) will probably do the trick; paraffin waxes; Nordel.... If you can tolerate a bit of aromatic solvent in your hexane then your choice will increase hugely. This might be useful as rather a lot of the hexane-soluble resins/ polymers are rather waxy.
Polyethylene and polypropylene will go into HOT solvent, such as xylene or decalin. Keep in mind that the hot solvent is quite flammable.
Lots of rubbers will dissolve in heptane. Polyisoprene, polyisobutylene, styreneic block copolymers. For that matter, polystyrene will also dissolve (extremely!) quickly in heptane.
You should be able to spin coat all of these, but it will take some effort to find just the right mix of concentration, spin speed, etc.
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