Solution behavior of ionomers. I. Metal sulfonate ionomers in mixed solvents

Abstract

The solution behavior of metal sulfonate‐containing ionomers has been investigated in various mixed solvent systems. Ionomers, such as lightly sulfonated polystyrene (sodium salt) and sulfonated ethylene‐propylene‐diene terpolymer (metal salts) are generally insoluble in typical hydrocarbon solvents, but readily dissolve when small amounts of alcohols or other polar cosolvents are present. At relatively low polymer concentration these ionomers display unusually high thickening behavior in nonpolar solvents when compared with nonionic polymers because of association of the metal sulfonate groups. The addition of modest levels of polar cosolvent markedly decreases the solution viscosity and gives rise to viscosity‐temperature relationships different from those of conventional polymer solutions. For example, such solutions can display vicosities which increase, are relatively constant, or display maxima or minima over broad temperature ranges. These observations are interpreted as arising from a temperature‐dependent preferential interaction of the cosolvent with the sulfonate groups. While these ionomers can be regarded as polyelectrolytes of low charge density, they do not display the typical “polyelectrolyte” behavior often observed in aqueous solutions. This anomalous behavior is attributed to the fact that the metal sulfonate groups are largely un‐ionized in solvents of low dielectric constant. Therefore, the solution behavior is dominated by ion pair interactions rather than free ions.

Polyelectrolyte Solutions: Phenomena and Interpretation

“…Their behavior reflects the high stability of ion-pairs and their tendency to dimerize in media of low dielectric constant. This dimerization is intramolecular in highly dilute solution leading to a chain contraction, but it leads at higher solution concentrations to intermolecular association and a sharp increase in solution viscosity (40,41).…”

A nanoparticulate raloxifene delivery system based on biodegradable carboxylated polyurethane: Design, optimization, characterization, and in vitro evaluation

“…4 The behavior of polyurethanes such as viscosity, conductivity and light scattering are changed by polyurethane molar mass and solvent polarity and distribution of ionic group in the polymer chain. [5][6][7] The synthesized carboxylated polyurethane can be dissolved in cosolvent system of acetone/water easily due to large anionic field strength of the carboxylated (ACOO 2 ) groups. 8 This effect is created by dissociation of ionic groups in polar solvents resulting in the expansion of the ionomer coil.…”

“…8 This effect is created by dissociation of ionic groups in polar solvents resulting in the expansion of the ionomer coil. [5][6][7] One of the most interesting biopharmaceutical applications for biodegradable polyurethanes is related to the use of this type of material to control the release of drugs. 9 In addition, the polycaprolactone (PCL), presenting in the soft segment of polyurethanes, shows permeability to small molecules such as therapeutic agents.…”

Hydrophobic Aggregation in Polyurethane Ionomer Solutions

“…Ionomer solutions are commercially very important, for instance as stabilizers for paint solutions and as coating materials. Though extensive studies have been performed in the bulk, solution properties of ionomers have only recently been investigated (1)(2)(3). It has been well established that ionomer solutions show two types of behavior depending on the polarity of the solvents used (4): 1. aggregation due to dipolar attractions between chain segments in nonpolar or low-polarity solvents, and 2. polyelectrolyte behavior due to Coulombic interactions in high-polarity solvents.…”