Sulfonation of polystyrene: Toward the "ideal" polyelectrolyte

• Published in: Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 2013-06, Vol.51 (11), p.2416-2424
• Main Authors: Coughlin, Jessica E., Reisch, Andreas, Markarian, Marie Z., Schlenoff, Joseph B.
• Format: Article
• Language: English
• Subjects: Applied sciences; Chain dynamics; Chains; Chemical modifications; Chemical reactions and properties; Crosslinking; Exact sciences and technology; GPC; kinetics; Life Sciences; Light scattering; molecular weight distribution; NMR; Organic polymers; Physicochemistry of polymers; polyelectrolyte; polystyrene; Polystyrene resins; Sulfonates; Sulfuric acid
• ISSN: 0887-624X; 1099-0518
• DOI: 10.1002/pola.26627

ABSTRACT Sulfonation of narrow polydispersity polystyrene, PS, standards remains the method of choice for generating polystyrene sulfonate, PSS, samples with defined composition. Although a variety of sulfonation techniques have been described, relatively little is reported on the material obtained, which is used for so many studies on the fundamental behavior of polyelectrolytes. Here, we show that powdered polystyrene treated with concentrated sulfuric acid (96%) at 90 °C without catalyst yields fully sulfonated PSS. Extensive characterization with 1H and 13C NMR as well as size exclusion chromatography coupled with static and dynamic light scattering shows no evidence of sulfone crosslinking or chain degradation under the conditions used. Though mono‐sulfonated as soon as it dissolves in the acid, the PSS contains about 6% meta substitution. Sulfonation kinetics for this heterogeneous reaction depend strongly on particle size, sulfuric acid content and temperature. For preparing perdeuterated PSS from the corresponding PS it is essential to employ D2SO4, as about half of the aromatic units undergo H/D exchange during sulfonation. The remaining ortho H/D may be exchanged with extended exposure to the concentrated sulfuric acid, but the meta site is deactivated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2416–2624 The sulfonation of polystyrene powder is carried out with concentrated sulfuric acid and an elevated temperature. Fully sulfonated polystyrene chains are obtained with no chain scission or crosslinking, as observed with size exclusion chromatography, dynamic light scattering, and elemental analysis. Kinetic studies show that particle size, acid concentration, and temperature strongly influence the conversion rate. Perdeuterated poly(styrene sulfonate) is also prepared with D2SO4.