POLYETHERKETONES BASED ON PARA-CARBORANE - SYNTHESIS, SULFONATION, AND MEMBRANE-FORMING CHARACTERISTICS

Polycondensation of bis(4-phenoxyphenyl)-1,12-dicarbadodecaborane with aromatic and aliphatic dicarboxylic acids in trifluoromethanesulfonic acid affords a new family of high-MW poly(aryletherketone-carborane)s . The polymers derived from 4,4'-biphenyldicarboxylic acid and 4,4'-ox ydibenzoic acid are both essentially amorphous when isolated, but the former undergoes an unusual cold-crystallization process beginning at, rather than above, its glass-transition temperature (267 degrees C), and melts at 386 degrees C. Solutions of the polycarborane derived fro m 4,4'-oxydibenzoic acid afford high-performance ultrafiltration membr anes when gelled in water, with molecular weight cut-off values in the range 9000-16 000 daltons. Poly(aryletherketone-carborane)s undergo q uantitative, structure-defined sulfonation in 98% sulfuric acid, resul ting in the controlled introduction of two sulfonic acid groups per re peat unit. The resulting ionomers are insoluble in water but readily s oluble in the lower alcohols, to give solutions from which thin-film c omposite nanofiltration membranes may be fabricated. Such membranes ex hibit water-fluxes and ion-selectivities which compare favourably to t hose of many commercial nanofiltration membranes. (C) 1997 Elsevier Sc ience Ltd.