RunPyroRun
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polyvinyl azide?
Been having trouble finding any information about polyvinyl azide (polyvinyl alcohol with some of the hydroxyl groups replaced by azide groups)
I figured if this was possible, it would at least get some passing mention in papers or energetics books. Most of what I've seen is in PVA modified
into a tri-block set up with some -OH groups, some -N3 groups, and another functional group thrown into the mix.
Could be pretty neat with the potential for a lot of azide groups for good energy release and the potential for some nice click chemistry
polymerization.
Please enlighten me on the deal of azidation of polyvinyl alcohol.
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Adas
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I think that polyvinyl azide has been discussed on this forum. They mentioned preparation from PVC and sodium azide in a solvent (acetone) from which
NaCl would crystallize and PVA would stay in solution, AFAIR.
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RunPyroRun
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Still hunting down the thread you mentioned, but I have seen some papers on PVC to PVAzide and it makes a whole lot of sense. I was just wondering if
it could be synthesized from PVAlcohol straight with a similar process using NaN3. Is NaOH formation even favorable?
Hydrazoic acid may be another route, with the formation of H2O being a lot more favorable. But hyrdrazoic acid isnt the best thing to be messing
around with.
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Adas
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Quote: Originally posted by RunPyroRun  | Still hunting down the thread you mentioned, but I have seen some papers on PVC to PVAzide and it makes a whole lot of sense. I was just wondering if
it could be synthesized from PVAlcohol straight with a similar process using NaN3. Is NaOH formation even favorable?
Hydrazoic acid may be another route, with the formation of H2O being a lot more favorable. But hyrdrazoic acid isnt the best thing to be messing
around with.
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Formation of NaOH is not favorable. Neither is formation of H2O when you use HN3. PVC powder is much easier to get. NaN3 might be the problem.
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RunPyroRun
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Thinking further on the subject, would it be possible to nitrate the PVA then add azide groups with a metal azide (such as sodium azide) forming
sodium nitrate.
PVA is nice in that, in addition to very high molecular weight polymer chains, its bristling with -OH groups, so that even if the polymer isnt fully
nitrated or azided, the remaining OH groups can contribute mechanically with hydrogen bonding and it absorbs certain liquids extremely well.
I'm weirdly obsessed with PVA right now, I know.
Thanks for the help!
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Adas
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Nitration would be very difficult unless you divide the PVA into smallest particles possible. Still, it would be poorly nitrated. But removing the
nitro groups to add azide groups would be a waste since you can use PVC for that.
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AndersHoveland
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| Quote: Originally posted by Adas | | Nitration would be very difficult unless you divide the PVA into smallest particles possible. Still, it would be poorly nitrated.
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Actually, polyvinyl alcohol is not as hydrophobic as other polymers, so the nitration acids may be able to soak further in, especially if the polymer
is in a loose (non-compact) form.
If methylene chloride is used as the solvent, it may be able to saturate deeper into the polymer and allow a more complete nitration.
Actually, this would be the formation of an ester, and can be favorable if the H2O is dehydrated out. A mix of HN3 and anhydrous HCl gas on the PVA
may be enough to form the azide.
Just my opinion here, but I do not think organic azides have the best sensitivity to energy ratio. There are many other families of energetic
compounds that are much less sensitive for the same power, or much more powerful at the same sensitivity. Azide esters tend to be much more sensitive
than ionic azides. If you are interested in packing nitrogen into a molecule, nitrogen-rich heterocycles are a much better way to go. There was
mention in another thread of a tetrazole polymer that could be made from polyacrylonitrile (synthetic wool fiber).
[Edited on 24-1-2013 by AndersHoveland]
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DubaiAmateurRocketry
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A PV-Azide polymer has been synthesised and characterized by this team.
The IS and FS is very related to RDX, they prepared it from PV-nitrate, and found it hard to fully converting it to PV-azide with around half
remaining as PV-nitrate
https://www.google.ae/url?sa=t&rct=j&q=&esrc=s&a...
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DubaiAmateurRocketry
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I also wonder if you can replace the Cl in those compounds with Azide groups
http://en.wikipedia.org/wiki/1,3-Dichloropropane
http://en.wikipedia.org/wiki/Dichlorobutane
[Edited on 4-10-2013 by DubaiAmateurRocketry]
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AndersHoveland
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Not by direct reaction, at least not under normal conditions. Chloroalkanes are very sluggish in undergoing nucleophilic substitution, in fact the
reaction rate is negligible (although there are exceptions in certain situations).
One idea may be a catalyzed Finkelstein reaction to transform those Cl into Br, and then displacement with NaN3. Choice of solvent is important here,
there several things that need to be considered, it is not a straightforward reaction.
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Dany
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@AndersHoveland
what do you mean by "normal conditions"?
the answer is yes. You can prepare PolyVinyl Azide (PVA) by direct SN2 reaction of PolyVinyl Chloride (PVC) with NaN3 in
dimethylformamide (DMF) by heating the mixture @ 55°C for 96h (4 days). below is the procedure copied from [1] (see page 233 in [1]:
Synthesis of Polyvinyl Azide 2:
Polyvinyl chloride (6.0 g) and sodium azide (31.2 g, 480 mmol) were suspended in DMF (150 mL) and stirred for 96 h at 55 °C. After cooling to
ambient temperature, the reaction mixture was poured on water (500 mL) and stirred for 24 h. The precipitate was filtered off and washed with water
and methanol. The solid was stirred in a 1:1 acetone/water mixture for 12 h, filtered off and dried under reduced pressure. 2 was obtained as dark,
rubber-like solid (5.1 g).
dec.: 189 °C.
also PVA can be prepared from Polyvinyl Nitrate (PVN) also by reaction with NaN3 in DMF (see [2] and the reference therein).
References:
[1] Stefan Sproll, Investigation of Nitrogen-Rich Polymers Based on Tetrazoles and Triazoles (PhD thesis, 2009)
[2] S.C. Mishra, Jyotsna Pant, P.K. Dutta and U.C. Durgapal, Def. Sci. J., 47(2), (1997), 131-137
link for reference [1]:
http://edoc.ub.uni-muenchen.de/11959/1/Sproll_Stefan_M.pdf
for reference [2] see attached file.
Dany.
Attachment: [2].pdf (746kB)
This file has been downloaded 770 times
[Edited on 4-10-2013 by Dany]
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madscientist
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| Quote: Originally posted by AndersHoveland |
Not by direct reaction, at least not under normal conditions. Chloroalkanes are very sluggish in undergoing nucleophilic substitution, in fact the
reaction rate is negligible (although there are exceptions in certain situations).
One idea may be a catalyzed Finkelstein reaction to transform those Cl into Br, and then displacement with NaN3. Choice of solvent is important here,
there several things that need to be considered, it is not a straightforward reaction. |
Nucleophilic Substitution under Normal Conditions with Exceptions in Certain Situations - Deoptimization of Early 20th Century Chemistry.
Sometimes a show opens with a stroke. Beer spills at the mic. Chunks spew across the drum kit. Guitarist tumbles dead off the stage - bad cocaine. It
happens.
Just don't encore with excrement striptease. At least not again.
The Finkelstein Reaction in the 21st Century: Novel Application of Sodium Bromide in Refluxing Naphtha. Why Not? Rasputin* et al.,
JACS 2014, Accepted.
I weep at the sight of flaming acetic anhydride.
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PHILOU Zrealone
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Possible just as it is possible to do 1,2-diazido-ethane from 1,2-dichloroethane, 1,2-dibromoethane or 1,2-diiodoethane and NaN3 in DMF or DMSO.
Terminal "primary" X-CH2- are required for this to occure easily...secondary -CHX- will be much harder for substitution.
Electro withdrawing group will increase the ease of substitution by leading to a more labile halogen...expect thus the compound to be lacrymatory and
toxic (related to war gasses)... X-CH2-EWG
EWG can be -CH=CH-, -C#C-, -CO-, -CO2-R, -Ar, -C#N, -NO2, ...
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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