Anion exchange membrane from glutamic acid 

while I have gotten room temperature crosslinking after leaving the solution out for 2 weeks and realizing I couldnt dissolve the hard plastic with water. I usually heat it up to speed the process. if you want to use this for a hydrogen generator then yea this works although this is mainly an anion resin and if you replace the glutamic acid with citric acid then it can be a cation resin. but the citric acid PVA mixture cannot crosslink at room temperature.

@@CatboyChemicalSociety I understand, and what would be the minimum temperature and cross-linking time of PVA with citric acid? I ask because instead of a cloth I wanted to use horticultural fleece, and it melts at a temperature above 115C

@@mati141551 gotta change your substrate because you need a temp of atleast 150C.

​@@CatboyChemicalSociety OK thank you for the information

microwaving helps make baking times shorter but yes because I have a gas oven what I do is let it get hot and turn it off and just let the residual heat bake it and pull it out 30 mins later.

yes I have one video on it from CaSO4 to H2SO4.

it was a very shitty mixture of plain glutamic acid and PVA which made an emulsion and didnt crosslink. The clearer goop is a proper mix of glutamate hydrochloride and PVA which after discovering later can crosslink even at room temps given a week since even long soaking in hot water was not able to clean the bowl!! The substrate was treated with PVC then soaked in NaOH like usual.

@@CatboyChemicalSociety Thanks for prompt reply, I am getting very interested in ionomer membranes.... so many things become possible!!

if you can manage to incorporate them into the structure of a polymer but its really better to use an amine or a nitro group monomer and convert to amine after polymerization then convert amine to quaternary amine using methyl iodide.

@@CatboyChemicalSociety Thank you

Brittleness is due to crosslinking and one of the ways to remedy this is with a good ratio of crosslinker(glutamic) to polymer (PVA) you'd have to experiment though. The golden brown color is one indication of crosslinking but the best test is to see if the coating dissolves in water post baking. You can make small test strips along with your main sheet to dunk in water after some time while you bake.

The more crosslinked the more brittle so maybe cut down on the amount of glutamic you used

@@CatboyChemicalSociety Thanks. I will try with a different cloth, maybe something less "spongy" than the one I used. I've mixed in 3.5g of glutamic acid hydrochloride with the PVA for 2 sheets of 200x200 but maybe they sucked in a bit too much . I'll try something thinner and see how it goes .

@@CatboyChemicalSociety Love the learning process 😉 Thanks for the reply.

@@thrdel reducing glutamic makes the membrane less crosslinked and less brittle but makes the polymer more hydrophillic. theres a nice ratio where it acts like a hydrogel and another where its like a soft plastic so much that I can make fishing lures out of the resin.

Take monosodium glutamate then 1st react with 1 weight equivalent of citric acid to precipitate glutamic acid which is poorly soluble. Then mix glutamic acid with 10% HCl minimal volume to dissolve or add corresponding 1 molar equivalent HCl for more accuracy.

Go buy msg from super market weight out citric acid 1:1 dissolve in 2 solutions mix together and glutamic acid precipitates and monododium citrate stays in solution. Putting in refrigerator or freezer crashes out more glutamic acid.

You can find cheap bags of MSG (monosodium glutamate) at any Asian supermarket, Ajinomoto is the main brand. Dissolve 1 part MSG in 4 parts water, and neutralize with the required amount of 1M aq. HCl. Heat to boiling with a dash of activated carbon, filter, let cool to room temperature, put in the freezer overnight and filter off the glutamic acid, which is of high purity. Wash the sparkling white crystals with some ice water. Glutamic acid prepared like this is of high quality. Attempts at recrystallisation will actually decrease purity and yield owing to the formation of pyrrolidone-carboxylic acid

Yes

ok so I still am yet to test these membranes out but if polyamides are favored over esters then this maybe a problem or a good thing. anyway if its bad then I can use this as an alternative to PVC precoat since polyamides are quite chemically resistant and if it has free carboxylic acid then this will be an amazing novel cation resin. I really wonder if I made a cation or an anion resin.

@@CatboyChemicalSociety if you have carboxylic acids, then H+/cation exchange membrane, non?

@@TeslaFactory yes but I also originally hope that the carboxylic acid form crosslinks with the PVA chains which hopefully give rise to free amines which are anion exchange. I however had the thought in my mind that there is a possibility of polyamide formation which would form a cation resin instead but one that maybe leagues better than crosslinked PVA. I will have to do more testing to determine if that is the case.

@@CatboyChemicalSociety I'm not sure which would be favoured, polyamides vs PVA-COOH Cross linking reactions, but would definitely be cool to hear your results! Really fascinating stuff :)

@@CatboyChemicalSociety Try to trace back the mechanism. As far as I am concerned, the mechanism of condensation between carboxylic acids and 1*/2* amines is an addition elimination mechanism. The carboxylic oxygen withdraws electron density from the carboxylic carbon, hence allows for nucleophiles to attack, after proton transfer you will get a -H2O+ leaving group. Due to the higher electronegativity of nitrogen, it is the better nucleophile and polyamide formation is favored. If you add a little bit of acid to it as catalyst, the goal is to protonate the carboxylic oxygen firstly so you make it a better electrophile, unfortunately however -NH3+ is a weaker acid hence it will protonate firstly and unfortunately destroy they nucleophility. You should try adding -SO3H moieties to your membrane, try a polycondensation with appropriate sulfonated arenes (idk, something like sulfonated benzaldehyde, benzoic acid or a copolymer membrane with polystyrene sulfonate) [edit] I was thinking, you can use the protonation of amines to your advantage to favor ester formation if you want. The browning additionally does not indicate crosslinking but dehydration so you will get some C=C double bonds

I mean my 1st video shows that

@@CatboyChemicalSociety thanks, I guess I missed that one

Yes but put it on an alkaline treated PVC substrate as shown in previous video. So it will be more chemically resistant

@@CatboyChemicalSociety for the last attempt what temperature did you use to esterify? also given this is an anion exchange membrane, is the calcium sulfate and sodium sulfate still necessary or can you just use calcium sulfate in both chambers? sorry if it is a dumb question but i think it only lets hydroxide ions through hence why the sodium sulfate is still necesary? or does the membrane also lets the sulfate anions?

@@japanjapan3102 140C is enough but someone who replicated these membranes got it to crosslink at 100C. Sodium sulfate is necessary and easily made by adding calcium sulfate into boiling NaOH solution. You can use NaOH directly mixed with CaSO4 in the cell with 2% by weight NaOH compared to CaSO4 but there will be a delay till sulfuric is produced which is not good since the anode chamber is either starter dilute sulfuric acid or pure water

@@CatboyChemicalSociety i guess what i don't understand is, if this only lets anion through then how can the sodium move to the cathode side in the production of sulfuric acid? sorry for the confusion

@@japanjapan3102 you put sodium containing stuff on cathode side only. If any sodium is in anode side then bisulfate is formed which is unwanted. The anode side is pure water or dilute sulfuric acid and cathode side is sodium and calcium sulfate or calcium sulfate with sodium hydroxide or sodium carbonate.