AN AROMATIC POLYETHER IN WHICH SEQUENCE-RANDOMIZATION LEADS TO INDUCTION OF CRYSTALLINITY - X-RAY STRUCTURE OF THE CRYSTALLINE PHASE [-OARCOARARCOAR-]N (AR=1,4-PHENYLENE)

High-temperature (330-degrees-C) polycondensation of 4,4'-dihydroxydiphenyl sulfone with 4,4'-bis(4-fluorobenzoyl)biphenyl, using diphenyl sulphone as solvent and sodium carbonate as base, leads to formation of an amorphous polymer (A) in which the monomer-derived subunits [-OArSO2Ar-] (''S'') and [OArCOArArCOAr-] (''K'') essentially alternate along the polymer chain. In contrast, the polymer (B) formed on replacing part (ca. 10%) of the sodium carbonate by potassium carbonate is partially crystalline, and sequence analysis by C-13 NMR indicates that the distribution of S and K units within a chain is now almost entirely random. The crystalline phase of polymer B is identified as [-OArCOArArCOAr-]n, and a structure is proposed for this phase on the basis of X-ray fiber studies, single-crystal X-ray oligomer data, and molecular-modeling/diffraction-simulation techniques.