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)

Abstract

High-temperature (330 °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 [-OArSOjAr-] ("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 13C 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-]", 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.

Poly(aryl ether) Synthesis

“…High temperature polycondensation of 4,4'-dihydroxydiphenyl sulfone with 4,4'-bis(4-fluorobenzoyl)biphenyl using diphenyl sulfone as solvent and sodium carbonate as base, led to formation of the expected alternating polymer sequence. Replacement of sodium carbonate by potassium gave the random sequence polymer (39).…”

Controlled variation of monomer sequence distribution in the synthesis of aromatic poly(ether ketone)s

“…It seemed possible that the observed variation in crystallizability between the three polymers could result from differences in their sequence distributions since transetherification with sequence randomization is known to occur during the nucleophilic synthesis of aromatic polyethers in which both monomer residues in the chain are activated towards nucleophilic attack adjacent to the ether linkage. 12,13 This possibility was confirmed by 13 C NMR analysis ( Figure 5), which showed useful diagnostic resonances in the range ¼ 160-162 ppm, corresponding to the aromatic carbons attached directly to ether oxygens. Polymer N1a shows only two peaks in this region, corresponding to the two different carbons of this type that would be expected in the simple alternating structure (EKEKmK) n (c.f.…”

“…This variability is shown to relate to the degree of sequence randomization during polycondensation, an effect resulting from reversible cleavage of the ether linkages during the growth of the polymer chain. 12,13…”

Microblock Ionomers: A New Concept in High Temperature, Swelling‐Resistant Membranes for PEM Fuel Cells

“…Monomer design considerations included a requirement that they contain no ether linkages activated by electron-withdrawing groups on adjacent aromatic rings, as these are known to cleave reversibly under high-temperature nucleophilic polymerisation conditions, leading to disruption and randomisation of the chain structure (the 'transetherification' reaction [26,27]). Furthermore, the substitution pattern of every aromatic ring had to be carefully considered to ensure synthetic accessibility, appropriate reactivity and, most importantly, for purposes of purification and solubility.…”