New high‐temperature polymers. VIII. Ordered benzoxazole‐ and benzothiazole‐imide copolymers

Abstract

SynopsisOrdered heterocycle copolymers of high thermal stability were prepared from aromatic dianhydrides reacted with aromatic diamines containing preformed benzoxazole or benzothiazole units. These ordered benzoxazole-imide and benzothiazole-imide copolymers were prepared in the form of their soluble precursor polyamic-acids, which, after fabrication to desired shapes, were converted to the thermally stable polymer. In general, these polymers are more resistant to air oxidation at elevated temperatures than are simple aromatic polyimides, and their thermooxidative stability is equal to or greater than that reported for benzoxazole or benzothiazole homopolymers. Unlike the o-hydroxyamide precursors to simple polybenzoxazoles, the amic acid precursors to benzoxazole-imide ordered copolymers do not require temperatures above 300°C to complete ring closure nor inert atmospheres to prevent polymer degradation during ring formation. Excellent self-supporting films and film coatings for metals were prepared. Selected compositions were readily spun to excellent fiber.

Rigid-rod polymers. 1. Synthesis and thermal properties of para-aromatic polymers with 2,6-benzobisoxazole units in the main chain

“…The crystal structure of 9 has been determined17 and showed the desired linear structure. Diels-Alder reaction of p-(phenylethynyl)benzoic acid18 (12) with tetraphenylcyclopentadienone (13). Compound 10 was initially soluble in hot methylene chloride but was no longer soluble after crystallization occurred upon cooling.…”

“…A series of 12 papers appearing in this issue reports the results of a research program2 sponsored by the U.S. Air Force and directed toward the development of new structural materials having low density, high strength, high modulus, and long-term retention of these properties at elevated temperatures. Research in the past 2 decades has led to numerous aromatic heterocyclic polymer systems having excellent thermal and thermooxidative stability.…”

Review of laboratory methods for the preparation of polymer films

“…in depth has also been used successfully for SBR emulsions (26). For viscous solutions, a Gardner knife (45,68,82) or a doctor blade (22,33,64,72,83,84) is usually employed. For instance, spreading of a 5% benzene or toluene solution of polystyrene on glass plates with a doctor blade results in films as thin as 0.0009 in.…”

“…Another technique describes the use of a few drops of hydrofluoric acid to the water in which the film is dipped (90). When the film tends to be brittle it is convenient to remove it from the glass plate while still plasticized with solvent (82).…”

Synthesis and characterization of alkyl chain containing polytriazoleimide/reduced graphene oxide nanocomposites

“…For instance, the introduction of an aromatic heterocyclic structure to the molecular backbone can obviously enhance the thermal and mechanical properties of PI. So far, many efforts on chemical modification of PIs structures have been done, such as the introduction of heterocyclic rings including both benzoxazole and benzoxadiazole, pyridine, pyrimidine, furan, and phthalazinone in polymer backbone, which result in good thermal and mechanical properties of these PIs .…”