Casting a Film on Water

One way to cast a film is on water. This is a great way to cast a film, because a nice, thin film is formed, it is easy to remove the film from the substrate, and clean-up is a snap! Here's what you do:

1. DO EVERYTHING IN THE HOOD!
2. Disolve your polymer in an appropriate solvent.
   • Choose a solvent which is not miscible with water (Why?)
   • Choose a solvent which is less dense than water (Why?)
   • Choose a volatile solvent (Why?)
   • Make the solution fairly concentrated (Why?)
3. Get a flat piece of glass (watch glass, petri dish, bottom of a beaker) and put a blob of water on it (about 1-2 inces in diameter).
4. Using a disposable pipette, place some of your solution on top of the blob of water (just until it runs off the side of the blob)
5. Let the solvent evaporate
6. Remove film from surface of blob and let dry

Pretty neat, huh? The water method works well most of the time, but what if your polymer is water soluble, or only soluble in solvents which are more dense than, or miscible with water? Go here to find one possibility.