SULFONATION OF SYNDIOTACTIC POLYSTYRENE FOR MODEL SEMICRYSTALLINE IONOMER INVESTIGATIONS

Syndiotactic polystyrene was lightly sulfonated in 1,2,4-trichlorobenzene using acyl sulfate complexes. The sulfonation efficiency of the acyl sulfate increased significantly when anhydrides containing long aliphatic groups were used to complex sulfuric acid. The high sulfonation efficiencies, relative to acetyl sulfate, were attributed to the increased solubility of the longer hydrocarbon complexes in trichlorobenzene. The incorporation of small quantities (less 3.4 mol %) of sulfonic acid groups onto the syndiotactic polystyrene backbone was found to have little effect on the glass transition temperatures of these new materials. However, a much more pronounced effect of sulfonation was observed in the ionomer crystallization. Increasing the level of sulfonation decreased the melting point, degree of crystallinity, and apparent rate of crystallization due to a rejection of sulfonated styrene units from the crystalline domains.