Halomethylated polysulfone: Reactive intermediates to neutral and ionic film‐forming polymers

Halomethylation of polysulfone (PS) with C₈H₁₇OCH₂X (X = Cl, Br) in the presence of SnX₄ (X = Cl, Br) led to PS–CH₂X (X = Cl or Br or both) (Scheme 1). Under controlled conditions, PS–CH₂X could be isolated and retains the good film forming properties of PS itself. Interhalogen exchange reactions occur in the presence of SnX₄ (X = Cl, Br) under anhydrous conditions (Scheme 1), or a quaternary ammonium phase transfer catalyst R^*R₃N⁺X⁻, under aqueous conditions (Scheme 2). The exchange reactions with R^*R₃N⁺X⁻, are favored when R = C₈C₁₀, and with R = C₄ only if n‐octanol is added; otherwise gelation occurs. Exchange in CHCl₃ is attributed to dehydrohalogenation (and generation of dichlorocarbene) of the solvent in the presence of tetrabutyl ammonium hydroxide. Further chemical modifications of PS–CH₂X by reaction with strong nucleophiles, led to hydroxymethyl polysulfone, acetoxymethyl polysulfone, and t‐butyl‐oxymethyl polysulfone (Scheme 3). Hydroxymethyl polysulfone sometimes gels under basic hydrolytic conditions and is best obtained by methanolysis of PS–CH₂‐OAc. Both PSCH₂OAc and PSCH₂O‐t‐Bu are very stable, and provide a way to generate PSCH₂Br on need by cleavage with HBr in acetic acid. Direct oxidations with DMSO or tetrabutyl ammonium dichromate (Scheme 4) or indirect oxidations (Scheme 5) produce polysulfone with pendent CHO, CO₂R and PO₃R groups. Finally, polysulfones with linker arms including, carboxy alkyl, hexaglycol or sulfonamido crowns are described (Scheme 6). The reaction products were characterized by ¹H‐ and ¹³C‐NMR. Double irradiation experiments, proved unequivocally, that the first substitution occurred on the B ring of the bisphenol A moiety (see Table I); the second substitution occurs on the A ring in position a. Thermogravimetric analysis generally shows for all modified polysulfones an extra transition at a lower temperature. The area of this band agrees generally with the values expected from calculated substitution degrees.