I am currently synthesising polymers in DMF through a simple Michael addition. In the current procedure, the polymer is isolated by precipitiation when added to cold diethyl ether (crashes out into a viscous mass when vortexed). After repeat washings with ether and overnight drying, the NMR data shows residual DMF still present in the sample.
As the polymer is vulnerable to hydrolysis, is there any way to fully remove the DMF without aqueous washes?
DMF is always a "two sided coin", this method of purification by non-solvent precipitation is not effective in DMF/Et2O even if is so far largely utilized(my opinion) but can be used to remove a large amount of DMF and followed by another treatment . Make long story short, My advice to you dialysis against THF or any other polar aprotic solvent like dimethyl sulfoxide. THF is ease to remove by vacuum or precipitation in hexane. But if you are using DMF it probably means a very polar monomer. Maybe if you provide more details we could fine-tunne the answer. Is it a amine and a vinyl group, for example ?
Hi Raphael, thank you for your helpful suggestion. Specifically, I am synthesising poly(beta-amino ester) formulations currently with diacrylate (bisphenol A glycerolate) and amine (4-(2-Aminoethyl)morpholine) monomers making up the polymer chain.
So first of all, You need to test the solubility of your polymer in some solvent which should be very miscible with DMF. The best one is probably water but it is not a option, alcohols could be also good but same problem of water, so THF should be a good start point, indeed THF is the cyclic version of Et2O if you think about, so for dialysis it is almost the same. For that approach is important to know average molar mass of your polymer. non-solvent/precipitation is more effective as higher the molar mass. So if your polymer are short chains they are pretty soluble and so more difficult to precipitate, it could be a problem for dialysis as well because the "cut-off" is based in a mean size of pores so the cut-off should be pretty lower than the Mn of your polymer. I suggest you to leave your polymer long time connected to a vacuum line, after this first precipitation. DMF is dificult to remove without heating, just vacuum but it could help. I already used acetone or methanol(not a option) to wash/evacuation cycles in rotavapor it drives the DMF out, or even Et2O since it is volatile solvent, think about other candidates which could fits your system/product. Worked for sucrose methacrylate, could work for you. So I give you some suggestion I hope they could be useful in your case. Best regards.
I believe you can use Heptane as it forms an azeotrope with DMF. It works pretty well.
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