Effect of structure on solution and interfacial properties of sodium polystyrene sulfonate (NaPSS)

Abstract Sodium polystyrene sulfonate (NaPSS) is synthesized by two different methods: one using free radical polymerization of sodium styrene sulfonate and another through post‐sulfonation of polystyrene. Both the solution and interfacial properties of the two polymers obtained from these two methods are different. The osmotic coefficient of free radically polymerized NaPSS is 20% higher than that of the NaPSS obtained from the post‐sulfonation method. Further, the free radically polymerized NaPSS has negligible interfacial activity at both air–water and toluene–water interfaces, as compared to post‐sulfonated NaPSS. The former type of NaPSS also adsorbs to a comparatively lesser extent at a solid–liquid interface. The enhanced hydrophobic character of post‐sulfonated NaPSS is explained on the basis of its intrinsically lower configurational entropy that results from the formation of intramolecular sulfone linkages, whereas the free radical method gives only a linear structure. Also, the intramolecular sulfone linkage will enhance the counter‐ion condensation and consequently decrease the osmotic coefficient of the post‐sulfonated sample. However, it is generally difficult to predict the exact degree of intramolecular sulfone linkage that may occur, as it depends on several factors. An attempt has been made to interpret some of the experimental data in the existing literature on NaPSS, which has mostly been prepared using the post‐sulfonation route. Copyright © 2006 Society of Chemical Industry