I have a sample containing a polymer resin completely dissolved in a DMSO solution. I want to determine the weight percentage of this solution. I have been thinking of eliminating/evaporating the DMSO and ultimately weighing the remaining polymer resin. Can anyone suggest a way of eliminating the DMSO from the solution or even better, a way of determining the weight percentage of my polymer solution without necessarily first eliminating the DMSO?
Addition of a non-solvent to the mixture can precipitate the polymer resin.So, either search for a non-solvent to precipitate the polymer or use an analytical method such as chromatography (GPC, FPC, ...) to measure the polymer percentage.
I might second Leonid suggestion, however, depending on the resin structure, less polar solvents such as acetone and chloroform might be a better choice. In this case however, you may experience fractionation, i.e. something will precipitate and something else will not.
Low temperature vacuum evaporation of DMSO will guarantee that all of the resin is recovered, but it is tedious and takes plenty of time to fully remove the solvent.
Liquid chromatography could be the best choice for analytical purpose. On the other hand, setting up the method can be tricky and relating peak area and resin concentration usually is very difficult. Additionally, you will never know the amount of resin that has too high a molecular weight to elute (you can even damage the column).
By taking into account the above considerations, I suggest using the evaporation method. If you don╒t know the resin structure, do it on a small sample of the resin solution by using the highest vacuum is available in your lab, at low temperature in order to avoid resin decomposition. In any case, weight the vessel at time intervals up to really constant weight.
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