A composite polymer solution comprising a homogeneous mixture of at least a first polymer solution and a second polymer solution; the first polymer solution comprising an amide solvent and a first polymer having a structure derived from the reaction of one or more amine monomers and a plurality of acid monomers, wherein i) the one or more amine monomers includes at least 60 mole percent 5(6)-amino-2-(p-aminophenyl)benzimidazole, based on the total amount of amine monomers; and ii) the plurality of acid monomers include those having a structure of; Cl—CO—Ar1—CO—Cl & Cl—CO—Ar2—CO—Clwherein Ar1 is a para-oriented aromatic group and Ar2 is a meta-oriented aromatic group, and wherein the plurality of acid monomers has at least 50 mole percent of the monomer containing aromatic group Ar2; and the second polymer solution comprising an amide solvent and a second polymer having a structure derived from the reaction of metaphenylene diamine and isophthaloyl chloride.展开▼
