Vacuum drying can be worse than ever, making the solvent boil at low pressure. So the bubbles seen are not necessarily due to air. What about using a surfactant and drying in room conditions ? If the sufactant is not enough, you should add a plasticiser. Its nature depends on that of the polymer you use.

Alain

Try cast in glass, Or use pressure.

@Alain Thanks. I have added plasticizer already still the problem exist. So, maybe surfactant or room atmosphere drying might work

Change your solvent with a bit higher volatility then the one you are using currently. For ex. i have casted PLGA using DCM where i do few bubbles i have not taken care of handling the polymer solution (mixing does tend to trap air inside the liquid, and due to high viscosity, the pressure inside the bubble is not strong enough to overcome the interfacial tension ) but by replacing it with acetone, i get bubble free thin films quite easily.

Also, vaccum drying is usually done to remove residual solvent. As said before, lower the pressure makes the solvent more volatile 

i to have same problem with my polymer solution can i just go for placing my solution in hot water bath.? weather h tat can help to get rid of air bubbles..?

Do you use single solvent or solvent mixtures?

i use acetone and i left it in room temperature for one week or more but when in proceed in moderately high temperature the bubbles come out and destroy everything I don't know what to do about it.