I am trying to dissolve lab-synthesized PLA films to observe the formation of a clear zone on an agar plate. For this purpose, I want to prepare an emulsion agar plate, thus the dissolution into water/buffer is necessary. I have tried the solvent evaporation method using dichloromethane with no success. The PLA films dissolved well in dichloromethane but precipitated out after sonication and after all the solvent has evaporated. I reduced the amount of PLA and increased the volume of dichloromethane yet the same thing happened again. I thought the thickness of the films may interfere with the dissolution, so I powdered the films using dichloromethane and methanol, followed by dissolution into dichloromethane, sonication, and solvent evaporation. Again, the PLA precipitated out. In my final desperate attempt, I dissolved the PLA powder into a buffer, sonicated the solution just enough to get the powder PLA dispersed in the solution, and make an agar plate with it. The resulting emulsion plate was far from expected, with powder PLA looked more like rough glitters than emulsion on the plate.

FYI, the PLA films were synthesized by another lab and they refused to provide more information on the polymer properties.

Any opinion is highly appreciated. Thanks!