chemoleo
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Copper Silk
You might have heard of this:
Cellulose can be solublised with the Schweizer's Reagent, which is an aqueous solution of tetraamin copper hydroxide (II).
Historically that solution was made by adding 20% NH3 to Cu filings, which contain a small amount of ammonium chloride, followed by bubbling air
through this.
Then, a deep blue solution is obtained, in which cellulose dissolves, to yield a viscuous solution of copper silk. When this is pressed through a
small orifice, into plain water (possibly acidifed), one gets very fine cellulose threads, which were used commercially.
Now I wondered, what the hell is the mechanism of solubilisation? I guess it's some form of complex, but why would it make it soluble,
considering these are still extremely long, chainlike molecules?
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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BromicAcid
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Look at this site here
http://www.woodrow.org/teachers/chemistry/institutes/1986/ex...
It has the ions in the solution and such. I googled around a bit and possibly the reaction is kind of like a detergent rendering grease soluble, the
detergent being the tetraaminecopper(II) hydroxide and that is in turn decomposed by the sulfuric acid, without the detergent the cellulose drops back
out of solution.
Just an eduacated guess.
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darkflame89
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Ah thats what i wanted to do. This actually yields a polymer called rayon, where the dissolved cellulose in the copper tetraamine(II) ions, form a
polymer which is deposited in sulphuric acid, where a strip of plastic is formed.
The cellulose somehow form chains of polymer via the complex ions.
Ignis ubique latet, naturam amplectitur omnem.
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chemoleo
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I wonder whether this process can be applied to solubilising other poly sugars, such as glycogen (purifyable from liver), starch, etc!
or even such things as polyvinylalcohol!
I was hoping someone was aware of the structure of the complex ion... but I guess it wouldnt be easy to study, as it is heterologous, and not a single
species - crystallography might be difficult with it...
PS nice link bromic 
[Edited on 11-3-2004 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Tacho
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Very interesting link indeed Bromic!
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Geomancer
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"Rayon" is the name for a variety of semi-synthetic fibers based on cellulose. The main types are acetate and viscose (acetate being the
cellulose ester whereas viscose is plain regenerated cellulose). Cuprammonium is rare due to (I think) environmental difficulties, its main claim to
fame having been being good for "silk" stockings. Interestingly, nitrocellulose "rayon" was once used for the same purpose. And
you thought nylons were a bad thing to wear in a fire.
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