Sciencemadness Discussion Board

M5 fiber?

clearly_not_atara - 17-6-2016 at 02:01

This remarkable polymer, poly(4H-diimidazopyridin-2,6-ylene-hydroquinon-2,5-ylene), shows properties broadly superior to Kevlar. It was discovered in the 90s, but DuPont bought the patent rights in 2005 and it hasn't shown up in the media since.

What's up? Are they protecting their aramid business, or is something wrong with it -- and is the synthesis really as simple as Wikipedia makes it sound?

AdamAlden - 26-6-2016 at 19:06

Things that are bullet proof do not make the government happy. If it would positively affect their relationship with the government and society they probably would have done something with it by now.

UC235 - 26-6-2016 at 19:14

The wiki page doesn't make the prep sound simple at all. The starting materials will probably be at least 10x, if not 100x the cost of kevlar's starting materials and it needs elaborate post-processing to achieve the desired properties. There are a large number of other engineering plastics used for situations where extreme temperature resistance/abrasion resistance are necessary that are likely cheaper and easier to produce and there is simply not a niche where M5 would be cost effective.

clearly_not_atara - 29-6-2016 at 13:18

Quote:
There are a large number of other engineering plastics used for situations where extreme temperature resistance/abrasion resistance are necessary that are likely cheaper and easier to produce and there is simply not a niche where M5 would be cost effective.


I guess I should clarify: the application I'm interested in is surfboards. Kevlar and Zylon are very problematic for surfboards because they're rapidly degraded by UV light, while UHMWPE is incompatible with epoxy resin (and basically every other composite matrix). So surfboards are made of fiberglass or carbon fiber.
Quote:
M5 fibers investigated as part of this work were observed to be stable after exposure to visible and ultraviolet light. After exposure to Zenon [sic] lamp for up to 100 hours, the M5 fibers retained essentialy all of the virgin fiber strength; by comparison, Zylon fibers lost over 35% of the virgin fiber strength at this exposure time.


Anywho, as long as I'm speculating, the dihydroxyterephthalate might be made by the mono-acylation (obviously nontrivial) of an acetaldehyde equivalent with chloroacetyl chloride in the gas-phase:

ClAcCl + [AcOH] >> Cl-CH2-CO-CH2-CHO [some conditions and catalysts]

or by the rearrangement of vinyl chloroacetate:

C=COC(=O)CCl >> ClCC(=O)CC(=O)

both of which produce the 4-chloroacetoacetaldehyde or a similar thing. This dimerizes to 1,4-cyclohexanedione-2,5-dicarboxaldehyde by deprotonation of the acidic carbon between the EWGs and reaction with the pendant chloroalkane. Dehydrogenation of this cyclohexadione gives 2,5-dihydroxyterephthalic acid. Aqueous base is not going to work (aldol reactions).

The 2,3,5,6-tetraaminopyridine might be made by the reaction of malondialdehyde with HCN and diallylamine:

RCOH + HCN + NR1R2H >> RC(NR1R2)CN (Strecker reaction)

HOCCH2COH + 2HCN + 2Aly2NH >> NCC(NAly2)CC(NAly2)CN

and cyclization of the dinitrile with NH3 to give a -C(=NH)NHC(=NH)- linkage (Pinner reaction), which is really a tetrahydropyridine in disguise:

NCC(NAly2)CC(NAly2)CN + NH3 >> N1=C(N)C(NAly2)CC(NAly2)C1=N

Dehydrogenation gives N3,N3,N5,N5-tetraallyl-2,3,5,6-tetraaminopyridine, which is deallylated to give 2,3,5,6-tetraaminopyridine.

I guess the precursors are just more complicated than p-phenylenediamine (which is sort of complicated) and terephthalic acid (which is stupid easy). But there's room for optimization, I think.

PHILOU Zrealone - 30-6-2016 at 13:39

Quote: Originally posted by clearly_not_atara  


The 2,3,5,6-tetraaminopyridine might be made by the reaction of malondialdehyde with HCN and diallylamine:

RCOH + HCN + NR1R2H >> RC(NR1R2)CN (Strecker reaction)

HOCCH2COH + 2HCN + 2Aly2NH >> NCC(NAly2)CC(NAly2)CN

and cyclization of the dinitrile with NH3 to give a -C(=NH)NHC(=NH)- linkage (Pinner reaction), which is really a tetrahydropyridine in disguise:

NCC(NAly2)CC(NAly2)CN + NH3 >> N1=C(N)C(NAly2)CC(NAly2)C1=N

Dehydrogenation gives N3,N3,N5,N5-tetraallyl-2,3,5,6-tetraaminopyridine, which is deallylated to give 2,3,5,6-tetraaminopyridine.

I guess the precursors are just more complicated than p-phenylenediamine (which is sort of complicated) and terephthalic acid (which is stupid easy). But there's room for optimization, I think.

You got lost in your own synthesis...better write a little more in extension...

R-CH=O + H-C#N + H-N(-R1)(-R2) --> R-C(-N(-R1)(-R2))-C#N (Strecker reaction)

O=CH-CH2-CH=O + 2 H-C#N + 2 (Aly-)2N-H --> N#C-C(-N(Aly)2)-CH2-C(-N(Aly)2)-C#N

N#C-C(-N(Aly)2)-CH2-C(-N(Aly)2)-C#N + NH3 --> HN=C(-NH2)-C(-N(Aly)2)-CH2-C(-N(Aly)2)-C#N

p-phenylenediamine is not complicated...as explained in the terephtalate tread of Boffis...it can be made from terephtalic acid via amidation (H2N-CO-C6H4-CO-NH2) or via azidation...so you have both terephtalic acid and p-PDA to make Kevlar.

p-phenylenediamine can also be done from terephtalic acid via dry distillation with Na2CO3/NaOH to make benzene, then nitration to nitrobenzen, reduction to aniline, then nitration to p-nitroaniline and finally reduction to p-benzene-diamine (p-PDA).



[Edited on 30-6-2016 by PHILOU Zrealone]