Synthesis and Characterization of Polybenzoxazinone and its Prepolymer Using Gas Separation

Polybenz‐3,1‐oxazinone‐4 (PBOZ) films are prepared via the thermal rearrangement of poly[(methylene‐bis‐anthranilamide) 4,4′‐diphenyloxidicarboxylic acid] (PAA) films by heating to 300 °C. PAA is synthesized by low‐temperature polycondensation. The PBOZ film exhibits excellent mechanical properties and a high glass‐transition temperature. Conversion of PAA to PBOZ leads to an increase in the fractional free volume as a result of thermal dehydration and cyclization during membrane formation and due to the removal of residual solvent. The excess free volume in the PBOZ film is approximately 3–4% of the total volume. The gas permeability and selectivity of the PBOZ film is higher than that of the PAA film. The thermal rearrangement of polymers is recognized as a suitable method to improve separation efficiency. The synthesis and physicochemical characterization of poly(benz‐3,1‐oxazinone‐4) (PBOZ) are discussed, which is prepared via the thermal rearrangement of its precursor polyamic acid (PAA). The PBOZ membrane contains excessive free volume as a result of its preparation. Thermal rearrangement of PAA leads to transformation in the morphology and improves the transport properties of the membrane.