Choice of nonsolvent in polymer purification by reprecipitation

Recently, I have synthesized new polymer. To purify the polymer, I tried reprecipitation. Because general nonsolvent is methanol, I dissolved the polymer in dichloromethane and reprecipitated into methanol. Methanol turned dark-red and was transparent, no precipitation was observed. Just in case, I tried filtration. Initially the dark-red methanol was filtered as it is, but shortly the filtration speed is significantly decreased and transparent and nearly colorless drops was observed. After 4~5 hours filtration was completed. Something looks gummy was obtained in the surface of filter paper, and after the methanol is evaporated I could recover some solids. I thought that this filtration did not go well because initially the dark-red methanol was filtered as it is (i.e. the color of filtrate was not changed). Because the polymer has polar moiety in the repeating unit, I tried to reprecipitate the polymer into hexane. In this time reprecipitation did go well and recovered powder. But regardless of the choice of nonsolvent as methanol or hexane, both the recovered polymers were completely undissolved in methanol. Although methanol does not dissolve the polymer, can it be ineffective in reprecipitation of polymer? The fact that methanol does not dissolve the polymer does not always correspond to effectiveness for polymer reprecipitation? And, I used relatively large amount of solvent in dissolving polymer, resulting in small particle size of precipitated polymer. Due to this, the recovery of polymer decreases because even after recovery there are some remained polymers in the filter paper. If I use small enough amount of solvent in dissolving polymer, can I get larger particle size of precipitated polymer?


