Film comprising a mixture of poly (M-phenylene isophthalamide) and copolymer made from (6)-amino-2-(P-aminophenyl) benzimidazole

1. A film comprising a mixture of at least a first polymer and a second polymer;

the first polymer being a 5(6)-amino-2-(p-aminophenyl)benzimidazole (DAPBI) 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—Ar 1 —CO—Cl & Cl—CO—Ar 2 —CO—Cl

wherein Ar 1 is an aromatic group having para-oriented linkages and Ar 2 is an aromatic group having meta-oriented linkages, and wherein the plurality of acid monomers has at least 50 mole percent of the monomer containing aromatic group Ar 2 ; and

the second polymer being poly(metaphenylene isophthalamide) (MPD-I),

the film having a MPD-I rich zone at the film center, a DAPBI polymer rich zone forming the outer film surface, and a transition zone between the film center and the outer surface that is a mixture of the MPD-I and DAPBI polymers.

2. The film of claim 1 , wherein the one or more amine monomers is 100 mole percent 5(6)-amino-2-(p-aminophenyl) benzimidazole.

3. The film of claim 1 , wherein the one or more amine monomers include metaphenylene diamine.

4. The film of any one of claims 1 to 3 , wherein the mixture of first polymer and second polymer contains 25 to 80 weight percent of the first polymer, based on the total amount of first polymer and second polymer.

5. The film of claim 4 , wherein the mixture of first polymer and second polymer contains 25 to 50 weight percent of the first polymer, based on the total amount of first polymer and second polymer.