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.