Films consisting of a rigid-rod polymer and thermoset resin matrixes mere prepared. Poly{(benzo[1,2-d : 5,4-d’]bis(oxazole-2,6-diyl))-1,4-phenylene} (PBO) in polyphosphoric acid (PPA) was blended with 2,6-bis(4-benzocyclobutene) benzo[1,2-d : 5,4-d’]bis(oxazole) (1), and films were extruded from these solutions. The coagulated films were soluble in methanesulfonic acid (MSA). After heat treatment at 300 degrees C, the films became insoluble in MSA. Crosslinked films were homogeneous and did not show phase segregation between the two components. These were composite films at the molecular level. Transmission electron microscopy (TEM) showed enhanced interlayer integrity and reduced microfibril separation for the molecular composite films as compared to normal PBO film. These films had significantly better torsion and tension delamination resistance. The incorporation of a second component did not sacrifice the tensile properties of PBO film. Thermal stability of these composite films was only slightly lower than that of normal PBO film.