Polymers having one or more sulfonic acid groups covalently bonded to one or more carbon atoms including the polymer are stabilized against thermal and hydrolytic degradation by reaction with an oxirane. The solid, gel-free hydroxyalkyl sulfonates thus formed are readily converted to thermoplastic ionomers by reaction with a metallic base or salt of a weak acid. The polymeric hydroxy alkylsulfonates possess a low melt viscosity and thus are readily mixed with neutralizing agents, plasticizers or other polymers and thereafter converted to ionomers by reaction with the neutralizing agent which is a metallic base or salt of a weak acid. The formulated solid gel-free ionomers are thermoelastic in nature and can be extruded, injected molded, and compression molded to useful products.