Realisation of siloxane ionomers by mild oxidation of alkylmercaptosiloxanes

New siloxane polymers containing pendant mercaptopropyl and methyl groups h ave been synthesized by an acid-catalysed sol-gel reaction. The mercapto gr oup was then oxidised to sulfonic acid using an excess of 3-chloroperoxyben zoic acid. This approach avoids the use of traditional strongly acidic sulf onating agents. Products with varying ratios of methyl and propanethiol/pro panesulfonic acid constituents have been characterised by FT-infrared and N MR spectroscopies, elemental microanalyses, thermogravimetry and differenti al thermal analysis and ion exchange titrations.