Process for producing aromatic heterocyclic polymer alloys

A method for preparing a molecular composite film comprising the steps of:

• A. forming a solvent mixture composed of (1) about 70 to 99 weight percent of methanesulfonic acid and (2) about one to 30 weight percent of a polymer mixture composed of (a) about 5 to 50 percent of a rod-like, aromatic, heterocyclic polymer and (b) about 50 to 95 weight percent of an amorphous, coil-like, aromatic, heterocyclic polymer;
• said rod-like, heterocyclic polymer consisting essentially of repeating units having the following structural formula:
• ##STR12## Wherein X is NH, N.phi., O or S, where .phi. is phenyl, and Ar is ##STR13## and n is an interger having a value such that the polymer has an intrinsic viscosity of about 5 to 30 dl/g as determined in methanesulfonic acid at 30.degree. C.;
• and
• said coil-like, heterocyclic polymer consisting essentially of repeating units having the following structural formula:
• ##STR14## Wherein x is NH, N.phi., O or S, where .phi. is phenyl and Ar' is ##STR15## and m is an integer having a value such that the polymer has an intrinsic viscosity of about 2 to 20 dl/g as determined in methanesulfonic acid at 30.degree. C.;
• B. introducing said solvent mixture into a casting mold positioned within an enclosed chamber containing water vapor;
• C. permitting said solvent mixture to absorb said water vapor for a period of time sufficient to form a precipitated film;
• D. recovering said precipitated film from said mold;
• and
• E. drying the recovered film.