Self-organization of sulfopolystyrene ionomers in solutions: Dependence on the polarity of the solution and the content of ionogenic groups in chains

Abstract

The self-organization of ionomers of sulfonated polystyrene containing different amounts of SO3Na ionogenic groups (0.5, 1.35, and 2.6 mol %) in three solvents (benzene, toluene, and THF) is studied via the methods of neutron scattering. It is shown that, in toluene, ionogenic groups form “effective” chains of up to 10–20 macromolecules owing to aggregation. In benzene, chains of both the PS precursor and ionomers are surrounded by volume solvate shells in the form of ∼4-nm-dia tubes that hamper interaction between ionomers via ionogenic groups. The tendency of ionomer chains toward aggregation in benzene is enhanced as the content of polar groups in chains is increased to 2.6 mol %. The diameter of solvate shells around chains decreases to ∼1 nm, and chains associate to form denser structures. In this case, the degree of integration of macromolecules turns out to be smaller than that in toluene. In THF, the processes of solvation and structuring of PS precursor chains are well defined and compete with tendencies toward association through ionogenic groups in solutions of ionomers. The formation of developed supramolecular structures in THF is hindered by the shielding of the potentials of interaction between ion pairs because of a high dielectric constant of the solvent.