Abstract: A method for preparing optical quality, thin films of polymers and co-polymers, as well as blends of such polymers or co-polymers with flexible polymers and co-polymers which comprises(a) preparing a solution of the polymer or co-polymer or blend in a suitable solvent;(b) forming a film from the solution;(c) cooling the thus-formed film to a temperature below the freezing point of the solvent; and(d) dissolving the solvent out of said film at a temperature below the melting point of the solvent.This method can be employed to prepare films of high optical clarity for electro-optical device applications. Because of their thermal stability, mechanical strength and chemical resistance, films prepared according to this method can also be used as filters and separation membranes.

Abstract: A method for preparing optical quality, thin films of rigid-rod polymers and co-polymers, as well as blends of such polymers or co-polymers with flexible coil-like aromatic heterocyclic polymers and co-polymers which comprises(a) preparing a solution of the rigid-rod polymer or co-polymer or blend in a suitable solvent;(b) forming a film from the solution;(c) exposing the film to a non-solvent vapor for about 1 to 5 minutes per micron thickness in the finished film; and(d) coagulating the film in a non-solvent.This method can be employed to prepare films of high nonlinear optical susceptibility for electro-optical device applications. Because of their thermal stability, mechanical strength and chemical resistance, films prepared according to this method can also be used as filters and separation membranes.