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.
A comparative study of metal − polymer complexes of Cu(I) with polybenzoxazinoneimide (PBOI) and its prepolymer imide-containing polyamic acid (PAA) as novel membrane materials for methyl tertiary butyl ether (MTBE) purification was undertaken. The structure, physical parameters and transport properties were characterized in detail to analyse the separation performance of the membranes and obtain new knowledge on the interdependence of the chemical structure and physical data with transport parameters. Thermally initiated conversion of PAA − Cu(I) to PBOI − Cu(I) was studied by TGA and DSC. The thermal conversion increases the polymer glass transition temperature and membrane density. Both polymers were applied to pervaporation separation of MTBE from methanol impurities. Membranes based on PAA are highly effective in MTBE purification and preferably permeate methanol. The transport properties of PAA − Cu(I) membrane are compared with those of known membranes.
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