Process for preparing a polypropylene-based sponge-like porous thin film

A method for preparing a porous polypropylene thin film, the method comprising:

• dissolving polypropylene in an organic solvent to form a solution under reflux condition;
• stirring the solution for about 5 to about 30 minutes;
• adding a cavity forming agent to the solution and mixing the solution until the cavity forming agent is well-dispersed therein, thereby forming a well-dispersed solution;
• placing a solid substrate onto a spin coating holder or chuck;
• applying the well-dispersed solution onto the solid substrate through spin coating to form a thin film on the solid substrate;
• collecting excess materials of the polypropylene and the organic solvent in a drain connected to a receiver;
• removing the solid substrate with the thin film formed thereon from the spin coating holder or chuck;
• subjecting the formed thin film to post-heat;
• peeling the thin film off the solid substrate;
• and
• extracting the cavity forming agent from the peeled thin film by washing the peeled thin film in an aqueous or nonaqueous solvent, thereby obtaining a porous polypropylene thin film with cavities, macro-voids, and micropores.