Precipitating a polymer solution into methanol

This is the basic technique for precipitating a polymer solution. This is done to purify the polymer by removing unreacted monomers, solvents, catalyst, and other low molecular weight materials. Methanol is widely used, but other solvents such as hexane may useful for certain systems. The objective is to add the polymer slowly, to a much larger volume of the other solvent, with a high amount of agitation. In this case I am precipitating 10 grams of a polyester, dissolved in 100 ml of dichloromethane, into 1,000 ml of methanol. Polymer solution is being added using an addition funnel. The precipitated polymer is then filtered and dried under vacuum. Non-crystalline polymers will tend to form a sticky mass rather than filaments or powder, but the purification is still effective if the material is added slowly enough and with strong agitation.

[@hasanuwanihalagedara4901]

Thanks much!

[@lidiapalha9070]

If you did this, would you have to do it three times. So like filter off the precipitate and than dissolve again in DCM and the precipate in methanol again.

[@PsmStyLePush]

hi i synthesid poly(acryamid-acrilic acid) co polymer. i want to powder form but my polymer dissolved in water. Do you think how can i take this polymer with powder form ?

[@anjanahere]

What is the instrument used here? Anyone pls tell

[@user-bu9ml4kd8x]

Hi. Could I ask you something?
I synthesized polyimide for my research. After synthesizing using 2 step; polycondensation and imidization steps, I poured a polyimide solution into methanol as much as slowly under stirring. Brown-color power was come out as result material. However, the color of methanol became also browny. I have been changing the methanol three times. But the color of solvent which contains polyimide powder does not maintain transparent own color. Is there any problem for my synthesis step or purification step?

[@erichall9907]

Hi, I am not familiar your polymer or procedure. But in general, you pick a solvent that the polymer is KNOWN to be soluble in, and then a precipitating solvent the polymer is KNOWN to be insoluble in. dissolve you polymer at about 10% in the solvent, and then when you precipitate, keep the volume added to the non-solvent no more than 10-15%. for instance, if you have 100 mls of polymer solution, you will need 1000 mls of non-solvent. then the only way to measure efficiency is to collect your precipitated polymer, dry it, and calculate your recovery. It should be over 50%, unless you polymer is very impure, low conversion, low molecular weight, or it simply doesn't precipitate. polymers that crystallize or have a lot of hydrogen bonding usually precipitate very well. high Tg polymers will give powder or filaments, and low Tg, non-crystalline polymers will be like chewing gum. finding the right conditions of solvent, concentration and temperature can be an art rather than a science, that is why you should try to find a known method that has been shown to work for a similar polymer. good luck.
Eric

[@user-bu9ml4kd8x]

@@erichall9907 Hello. Eric. First, thank you for giving me a detailed answer. I got it to some extent because of you. Can I ask something? The answer said "high Tg polymers will give powder or filaments, and low Tg, non-crystalline polymers will be like chewing gum". I understood expression like powder or filaments. But I didn't for like chewing gum.. Could you explain about it more detail?

[@erichall9907]

@@user-bu9ml4kd8x soft and sticky, and sticks together, like rubber

[@cookerytime885]

Hi, i want to ask some questions about this video.... From the description, you dissolved 10 g poltester into 100 ml dichloromethane... And then you used methanol for precipitating, how to choose he correct solvent for precipitating polymer ?
N hexane is nonpolar solvent and methanol is polar (?)

[@erichall9907]

good question, it all depends on the polymer, and what you are trying to remove by precipitating. the first thing to consider is the polymer solubility- you need to pick a solvent that the main polymer is not soluble in. some common choices are methanol, ethanol, hexane, etc. the second consideration is you want the polymer solvent (DCM in this case) to be soluble in the precipitating solvent, along with the impurities you are trying to remove form the polymer. So the DCM and impurities stay in solution, and the polymer precipitates out.

[@cookerytime885]

Oh ok, thank you for the explanation !!

[@ivanfelipevaldivieso]

​@@erichall9907 Hi Eric, which are your recommendations for hydrophylic polymers in aq solution??

[@erichall9907]

@@ivanfelipevaldivieso an alcohol, depending on the polymer, methanol, ethanol, or IPA, whichever one the polymer is not soluble in. good luck

[@ivanfelipevaldivieso]

@@erichall9907 Im synthetizing a variety of co-polymers so i dont have so much info, nevertheless they are all water soluble ... so im thinking on hexane, xilene or +3C alcohols. Thanks!!