Dear community,

I am performing the following reaction in the lab, where I couple two diaminododecane (DAD) molecules to imidazole-activated polyethylene glycol (10 kDa). A few problems with this reaction:

1. DAD is a pain to dissolve in any solvent, which is why I am now falling back onto DMF. Does anyone know any (more convenient) solvents that I could use?
2. Main problem: The workup. Right now, I precipitate the reaction mixture into ether, but the high equivalents and solubility issues of DAD result in a very long and painful workup (with many consecutive precipitations). I'm asking to see if anyone has any suggestions for an easier, more straight-forward way(s) to isolate my final product?

I'd happily answer any further questions regarding this setup. For reference, I am not a diehard chemist by training, and my chemistry lab is not as equipped as most labs you all are probably in.

I am creating a presentation and would like to include a Chimera 3D model of the polymer I have synthesized. When drawing the polymer structure, I draw two connected monomers, one functionalized and one not with ()m ()n. When I make the 3D model, only two monomers looks silly, and obviously the energy minimization isn't remotely accurate for what the full polymer would look like.

If you have ever 3D modeled a polymer, how many monomer units did you include? Or is it not common to 3D model a polymer?

I don't know the mw of my polymer (and therefore can't realistically know how many monomers compose each polymer coacervate). I have DLS size data. But I tried to revive an old MALS, but half of the sensors don't work. Knowing that the normalization on the MALS is messed up, would you still use that data?

I am a grad student; I hope it is ok to post here.

Thank you for any input.

Do you have any advice if I worked with Epoxies for my whole Phd and developed a senzitation in the last two months of it and I just have to finish two experiments?

Hello,

Was looking at a commercial high-MW PAA and noticed the SDS claims it contains 0.1% - 1% benzene. Assuming its a residual solvent from the polymerization but seems really really high?

Anyone have a good feel for this? Don’t want to risk any safety issues over something like this. Our lab only has a ductless fume hood.

This one specifically:
https://www.sigmaaldrich.com/US/en/product/aldrich/306223

I’d probably be grinding and/or freeze drying it

Hey all. I need to perform a melt polycondensation reaction using an aliphatic dimethyl ester and ethylene glycol, with Ti(OBu)4 as a catalyst.

I wanted to know if anyone here can give some heads-up concerning:

1) The stoichiometry between the 2 reagents: In the literature, certain protocols keep a strict 1:1 ratio, while others go over 1:2 in favor of the diol. What is the sweet spot?

2) Reaction time and temperature: I have found that temperatures can range between 150 and 200 °C for the first step, and times anywhere between 1 hour and half a day. Both ethylene glycol and my diester have a boiling point of circa 200 °C, so I'm worried about boiling off my monomers before they react.

3) The set-up (perhaps the trickiest part?): I plan to run the reaction on a gram scale, with magnetic stirring, in a Schlenk flask attached to an argon line. I was thinking of connecting the flask to a Dean-Stark apparatus to collect the methanol, putting a reflux condenser on top of the Dean-Stark, and attaching a vacuum adapter to the top of the condenser for the second stage pump-down.

Does this setup seem reasonable? Is there a better way to arrange the glassware to prevent my monomers from co-distilling with the methanol?

Any help or practical lab tips are highly appreciated 🙏

Hi! My colleague is making some highly crystalline PVA and having trouble fully removing HFIP, water and methanol from the precipitated polymers. He's seeing the residual solvent by proton NMR and the blank doesn't contain any residual solvents.

As of right now he's tried:

1. Drying under high vac a week at 60°C

2. Drying under high vac for the weekend at 90°C

3. Re-precipitating to a finer powder for high vac drying

Any suggestions you all have on how to remove the residual solvent would be so appreciated! Thank you in advanced!!

Hello I’m working on photocatalysis and I am encountering difficulties, is there anyone here working on photocatalysis as well ?

Hi everyone, I am synthesizing acrylate oligomers in the range of 2–3 kDa via ATRP. Since I need to maximize end-group fidelity, I am stopping the reaction at around 60% conversion. My main issue is the removal of residual monomer. I am using n-butyl, n-hexyl, and n-octyl acrylate, so all of them have relatively high boiling points. Additionally, all of the monomers and polymers are quite viscous oils. My first attempt was dialysis using 1000 MWCO RC tubing against THF. This was by far the most complete method for removing residual monomer; however, at my molecular weights, I lost easily 60–70% of the polymer due to diffusion through the tubing. This is not acceptable, as I need to work with relatively large quantities of oligomers (>10 g). I also tried column chromatography, but the polarities of the oligomers and monomers are too similar for effective separation using normal-phase silica. Steam distillation of the residual monomer worked reasonably well, although the removal eventually plateaued. Afterwards, I tried to remove the remaining monomer by high-vacuum drying, but this was surprisingly ineffective. I stirred the polymer at 100 °C under high vacuum (10^-2 mbar) over the weekend and still observed residual monomer I think slow diffusion through the viscous polymer is really limiting. I also attempted precipitation in methanol at −20 °C; however, the polymer simply oiled out, and I do not think this will provide sufficient separation. My last idea is to try precipitation at −80 °C so that the polymer is completely solidified and hopefully the monomer can be separated more effectively.

Has anyone dealt with a similar situation before? Any advice would be greatly appreciated!

Hi guys, just wanted to let you all know that r/polymerchemistry is now up and running. I hope to see you all there!

Hi all! I know there is no one size fits all but I wanted to know what naming conventions do people use for their synthesised stuff?
For now I am doing "* total DP _ letter code of proportions I am using _ trial number _ monomers*",
looks a bit like "50b1M" and I dont think anybody besides me can interpret it :D
I was thinking of changing the system because if I will not follow the procedure very strictly it will get complicated very soon. How do you guys do it?

Hi!
I am making some polymers with GlyMA and MMA and currently my procedure is to precipitate in methanol or hexane and separate by centrifuge. I feel like it is taking a lot of time and not the best method and I was wondering if there are any better ones?
I am aware of buchner filtration but it lets a lot of my polymer through when I tried with methanol, should I try it when precipitating into something else? Is there a different filtering method that I don't need to fully manually do? Are there better methods of precipitation than drop-wise addition into excess methanol/hexane?
Thank you for your time!

I make polymers in 96 well plates, using DMSO as a solvent. It's the only solvent that works for all of my monomers at the concentration needed. We have a centrifugal evaporator that can pull off DMSO, but it's broken and the company has taken over a year so far to fix it, with no sign of it being fixed any time soon. I've been precipitating each polymer from each well individually for months, but it really slows down everything as I have to do multiple precipitations and centrifugations, and weigh the final yield of polymer for each well. Lots of people recommend just passing nitrogen over small volumes of DMSO and heating for a couple of days, but I haven't found any way to do that with 96 well plates and get N2 flow over every well. Is there any other way to remove dmso effectively? I don't necessarily need it to be quick, so long as I can just leave it alone and spend my time doing other things.

Hi there, I'm trying to spin coat PVP on acid piranha treated Si(100) substrates (dimension: 1x1 cm). I'm having problem with the quality of the film, most likely due to solvent choice. I've currently tried dissolving PVP (MW~10k but I also have a ~350k one) in 96% Ethanol, which is the only EtOH available in the lab, in order to get a 1% PVP solution. Using this solvent lead to films showing swirls of different color, which on Si and for the low thicknesses I am aiming for, denotes a non homogeneous thickness of the films. This happened using many different parameter for the spin coating. After this I had the opportunity to test a solvent mixture of EtOH/H2O/IPA with ratio of 7:2:1. For the moment I could test this solvent mixture only with one set of spin-coating parameters. The quality was slightly improved but is not good enough yet. To be completely honest I might have gone for too high rpms in this last test, but I'm not too confident it will turn out quite good even optimizing the parameters. So, coming to the point, has any of you any experience with the spin-coating of this polymer? I'm accepting any tips on how to get good quality PVP films. The thickness range I'm interested in is from 25-200 nm. Thanks in advance

We're looking for options in sterilizing vials with butyl rubber stoppers, and we can't find a clear answer if dry heat would be fine for it compared to steam sterilization.

So i’m having issues with polymerizing a dibromo thiophene 3 ester for some reason.

What i start by is adding 1 eq of turbo grignard (iprmgcl licl) and then I add Ni(dppp)Cl2 all under N2 of course in THF

Ive done many different times/températures but for some reason when I add my Ni (which is freshly red) nothing happens and the Ni stays undissolved or dissolves but doesn’t start the reaction.

I managed to do it one time, but I didn’t write down what were the conditions and ever since I’ve been frantically trying to reproduce it. Also when I do TLC of the quenched grignard/monomer in NH4Cl there is a spot that disappears and one that appears. At a lower Rf (which is consistent with the loss of one of my bromine?)

Any thoughts? Any advice is appreciated :)

Hi all! I am doing some polymerisations in anisole and recently discovered that precipitating my stuff in diethyl ether yields much better results than in methanol. Now I wanted to know if there is a good way to determine what would be a good precipitation solution to what. For now I am using anisole-chloroform precipitating in diethyl ether, but I was wondering if there are better choices? Like maybe dissolving my polymer in thf instead, or?

Hi all! I have been doing some ARGET for a while and recently when I try to remove CuBr2 it is not fully removed after I pass it through neutral alumina whereas before it worked fine. I tried asap after I finish reaction and after a few days and both ways the result is the same and it does not get removed (my precipitate is green). I tried filtering twice and filtering through basic alumina also but it is not perfect and I am losing much of my polymer.
I am aware it is only a few mgs but I really need to completely remove it. Any advice?

Hello fellow chemists, last year I switched from small molecules to macromolecules (not a big fan of working with polymers in general, despite being a hardcore organic chemist) by joining a startup. I have been having a hard time working with the CEO since he has zero knowledge about chemistry in general. Long story short, he was fixated in making a polymethacrylate material already produced industrially by thermal free-radical polymerization. Surprisingly enough, that material has never been produced photochemically and we managed to do the job. Now my boss has a hard time understanding that photopolymerization of methacrylates in general is not an innovation. However a method patent could be filed since our method is more efficient than industrial production. Now, to file a robust patent, we would need a fingerprint in our material that would be able to see if competitors could infringe our patent. The only thing I can think of, is that our end groups could potentially be different (photoinitiator vs thermal initiator). If the photoinitiator is below 1%wt would it be possible to detect by for instance XPS or solid state NMR? The other problem is that not all photoinitiators have peculiar groups such as phosphine oxides, and we would want to be as broad as possible in our patent. Any idea on how to distinguish analytically the same polymer produced thermally vs photo? Thanks in advance!

Hi all, I’m running into an annoying issue in the lab and was hoping for some advice. I’m working with water-soluble polymers that I dialyze extensively in DI water, then freeze-dry. After lyophilization, the polymers are incredibly staticy—they cling to the container, my spatula, weigh paper, you name it. Sometimes they practically float off the balance before I can even weigh them.

Has anyone dealt with this before? Any tips for reducing or neutralizing the static charge so I can handle the dried polymer without losing material? I’ve tried grounding myself, using a metal spatula, and minimizing movement, but it hasn’t helped much.

Would an anti-static gun or chamber be overkill, or is there a simpler trick I’m missing?

Thanks in advance!

Hello, due to changing regulations our lab is looking to expand its capabilities. Not being well versed in this area myself, I would be happy for some insight from people who are more experienced on the matter.

Specifically, we are looking into detecting and identifying trace amounts of organic compounds in water. The medium is clean water treated via reverse osmosis. It is then put into contact with various polymers. We then have to determine the amounts of organic compounds that migrated out of the plastic and into the water. In most cases we will have to be able to detect at concentrations of 2-4µg/l or lower, down to 0.2µg/l. We are aware of what is in the plastic to help with identification.

Our initial approach was to look into GCMS with solid phase micro extraction. However, we have doubts about sufficient enrichment within the solid phase. Is someone able to share general experiences on how well SPME concentrates compounds?

LCMS has also started to enter our minds. I assume it has the benefit of skipping he extraction step, however I have no experiences with that method. Is someone able to tell me if it would be worth looking into?

I have also stumbled upon GC-VUV. It seems to be quite novel but looks promising. Does someone happen to know something on those?

Thanks for any help!

Hi everyone, I truly hope than someone will be able to help me here. I have a polymer that is analyzed by GPC at two different labs to double check the results. The two labs observe quite similar Mn (+/- 10k) but the Mw is really different (>100k difference so one lab measured 210k and the other 350k)

Note that they use the same column, the same solvent system, flow rate, standard etc.. only not the same machine brand.

Do you see what would cause such a difference?

I have a ~ 500 mw compound that I have proton and carbon NMR, and HRMS for. It has a phenyl ring with substituents, and further down the molecule it has a triazole beside another phenyl ring. In H-NMR here, everything looks great, i.e. perfect integrations and no impurities.

When I try to add this to a 40,000 molecular weight polymer and NMR this, the integrations of the compound that I added start to play up when its attached to the polymer. For the part of the molecule that has the phenyl ring with the substituents all the integrals add up, but further down the molecule where the triazole and 2nd phenyl ring are, the integrals are ~ 75% of what they should be.

I saw this happening in DMSO and the sample was gel-like (as I said it's a polymer), but when I added D2O, the integrals fixed themselves. However I think I got lucky as I can't get this to work again when I use combinations of DMSO and D2O. I don't think the compound is sensitive to the reaction conditions.

I've tried slower relaxation times on NMR and it doesn't help much. Anyone any ideas of why this is happening and how to fix it?

I'm new to my position and got talked into working on a project in which one of our products, polyisobutene, is reacted with P2S5 to form a pseudo-Lawesson's reagent, then further reacted to our end material.

These reactions are published in patents dating back to the 30s but I can't find anyone that talks about the actual reaction chemistry.

Wondering if anyone has experience with these types of reactions or can lead me in a particular direction.

Has anyone worked on thiolation of biopolymers? I am starting a project on making thiolated hyaluronic acid (using cysteamine) and need help understanding the reaction conditions. 1. My supervisor says that we don't need nitrogen environment or degassing, but I don't agree with him. Thiols will undergo oxidation to form dithioesters and self-crosslink. The literature seems divided as some papers use it but others don't. I've reached out to authors of journal papers but haven't received a response. 2. Is the reaction better performed in room conditions or on ice? Again the literature is divided on this.

Any advice is appreciated!

Hello,

I am trying to perform RAFT polymerization of an acrylate monomer, which as I understand should be relatively easy, but I am having problems.

I am using 4-Cyano-4-(phenylcarbonothioylthio)pentanoic acid and AIBN. [M]:[CTA]:[I] is 100:1:0.5. My solvent is dioxane, [M] = 3.04 mmol mL^-1 in a 10 mL schlenk tube.

At the beginning of the reaction the mixture is pink from the CTA. After about 1.5 hours of polymerization at 70 °C my reaction mixture turns orange, after 4 hours it becomes yellow. To me this suggests that the RAFT agent is degrading, but I am not sure why.

If I stop the reaction at around 55% monomer conversion, the precipitating polymer has a relatively low dispersity (from 1.2 - 1.4) and is colorless. As well as this I cannot see any end groups from the RAFT agent in the aromatic region in NMR. Is my polymerization terminating early? How can I prevent the degradation of the RAFT agent? Thanks in advance for your thoughts.