Synthesis and physical properties of sulfonated syndiotactic polystyrene ionomers

Sulfonation of highly stereoregular syndiotactic polystyrene has been accomplished in 1,1,2‐trichloroethane and chloroform (60/40 v/v) mixed solvent. FTIR spectroscopy was used to confirm that the sulfonated syndiotactic polystyrene was the product of the sulfonation reactions. Sodium, potassium, zinc (II), manganese (II) and cobalt (II) salts of the sulfonated polymers exhibited behaviour indicative of strong interactions. FTIR spectroscopy and DSC data showed that the roles of the cation–anionic site interactions in alkali form and transition metal form ionomers are somewhat different. The DSC data also showed that the alkali metal cations had more pronounced effect on T_g than did the transition metal cations. In addition, the crystallization behaviour of the ionomers with a low degree of sulfonation also exhibited considerable differences in comparison with the neat syndiotactic polystyrene. The melting points (T_m) and the degree of crystallization (X_c) were significantly lowered by the presence of the sulfonic acid groups or the sulfonate metal groups. Moreover, the ionomers were more thermally stable and more hygroscopic than the unmodified polymer. © 2001 Society of Chemical Industry