Get a anhydrous diethylether bottle out of the refrigerator (most likely they are already in the freeze), that would do!

Yeahhhh, thanks for your solution ^ ^

Oh, but I did the experiment without seeing any change , it has no precipitate or a little ...

Did you check your monomer conversion by GC or NMR? Maybe you have very short oligomers that do not precipitate easily... In the meantime, you can evaporate the solution, re-dissolve in a small amount of solvent and add dropwise to cold ether (keep it in the freezer for a while) under stirring. In addition you can put your beaker with cold ether in an ice-bath during the precipitation. Success!

yeah, I tried the same and got success. I thought about the short oligomer. Finally, I got the polymer which was precipitated in the frozen ether! ^ ^

Great, I'm happy it worked out well!

Cheers