I am trying to dissolve PEES polymer using DMAc solvent, but the solution has some solid lumps at the bottom. What could be the cause, should I change the solvent and use NMP?
Did you try to do sonication to help the dissolving? I believe DMAc and NMP are very similar for dissolving PEES.
NMP AND DMAC ARE GOOD SOLVENT FOR PES POLYMER. I HAVE USED THEM BEFORE. TRY TO DO ULTRASOUND FOR 10-15 MINUTES THEN INCREASE THE SPEED OF MIXING. YOU WILL SEE THE POLYMER AND SOLVENT ARE MISSIBLE
@Muayad Al-Shael, dissolving PES is not a problem. The polymer I am referring to is PEES not PES
Based on http://polymerdatabase.com/polymers/polyetherethersulfone.html
Hildebrand Solubility Parameter of PEES is ~23.5 (MPa)½
Perform further research to determine Hansen Solubility Parameter data.
NMP Solubility Parameter is ~22.4 as per Eastman Chemical Tech Data Sheet
Hansen solubility parameters @ 25°C
Dispersion 17.6 (MPa)½
Hydrogen Bonding 7.0 (MPa)½
Polar 12.0 (MPa)½
Total 22.4 (MPa)½
DMAc Solubility Parameter is ~22.7 as per Eastman Chemical Tech Data Sheet
Hansen solubility parameters @ 25°C
Dispersion 7.87 (MPa)½
Hydrogen Bonding 10.2 (MPa)½
Polar 11.5 (MPa)½
Total 22.7 (MPa)½
As a general rule of thumb, they are same level of magnitude within 1.0 total, in simple terms, they would be at least swellable within both solvents. Settling is most likely the HMW polymer or impurities in polymer whereas the solubilized portion is likely the LMW portion of polymer and/or oligomers. A >0.5 difference Chi value suggests neither is ideally suitable solvent in neat solvent system. DMAc was the preferred choice based on total Hildebrand SP. A combination solvent system may be tried to increase solubility parameter of solvent system.
I haven't worked with PEES, but at least for PES, NMP is a weaker solvent. If it's similar to PES, DMF or DMSO should be better solvents. You can also try to heat up the solution. What concentration are you using?
@Fernanda Ghiggi I'm working with 15% to 22%. I will try DMF and DMSO. Thank you
Maybe I will try to use the combination of NMP:DMF such as 3:1 ratio wt.%. However, I try to dry polymer to be sure that there is no moisture.
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