Effect of Different Low-Molar Mass Electrolytes on the Viscometric Behaviour of Sodium Polystyrenesulfonate in Methanol–Water Mixed Solvent Media Ajaya Bhattarai, 1,2 Bijan Das* 2,3 Summary: Precise measurements on the viscosities of sodium polystyrenesulfo- nate (NaPSS) in water as well as in methanol–water mixed solvent media have been reported in presence of NaCl, KCl, NaBr and KBr having concentrations of 0.1 and 0.5 mol.L 1 at 308.15 K with the polyelectrolyte concentrations in the range  0.001 to  0.012 eqv L 1 . The reduced viscosities of the polyelectrolyte solutions vary linearly with polymer concentration for all the systems investigated which enabled us to determine the intrinsic viscosities of sodium polystyrenesulfonate in methanol–water mixtures using the Huggins equation. The coiling of the polyion chains are found to increase in the order: NaPSS-NaCl < NaPSS-NaBr < NaPSS- KCl < NaPSS-KBr. The solvodynamic dimensions of the polyion coils are found to be reduced as the relative permittivity of the medium decreases. The present study also indicates that the polyion structures become more compact with increasing salt concentration in the medium. Keywords: intrinsic viscosities; methanol–water mixed solvent media; reduced viscosities; sodium polystyrenesulfonate Introduction The addition of a low-molar mass electrolyte (NaCl) to the polyelectrolyte solution resulted in shielding of the ionic sites with a reduction of the coil dimensions and drastically lowers the value of the reduced viscosity. Finally a situation was reached when there was an excess of NaCl ([NaCl]  0.10 mol.L 1 ), the reduced viscosity varies linearly with the polymer concentration similar to that for a neutral macromolecular solution, thus en- abling us to determine the intrinsic viscosity using the well-known Huggins equation [1,2] h sp =c P ¼ h ½ þ k H h ½ 2 c P ð1Þ where h ½ is the intrinsic viscosity describing the solvodynamic behaviour of the polymer molecules in solution, c P is the polyelectro- lyte concentration and k H is the Huggins constant which is a characteristic for a given polymer-solvent system. A number of studies dealing with the effect of different low-molar mass electro- lytes on the viscosity behaviour of poly- electrolytes have been reported in aqueous solutions. [3–10] However, systematic inves- tigations of the effect of medium on the viscosity of polyelectrolytes are relatively scarce. [11–16] The present chapter describes a comprehensive study on the influence of different salts with varying cations and anions on the intrinsic viscosities of NaPSS in methanol–water mixtures. The viscosity data have been analyzed to obtain informa- tion as to the polyion chain conformation 1 Department of Chemistry, M. M. A. M. C., Tribhuvan University, Biratnagar, Nepal 2 Department of Chemistry, North Bengal University, Darjeeling, India E-mail: bijan.chem@presiuniv.ac.in 3 Current address: Department of Chemistry, Presidency University, Kolkata 700 073, India. Macromol. Symp. 2016, 366, 8–13 DOI: 10.1002/masy.201650041 8 | ß 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com