Morphological Studies of Lightly Sulfonated Polystyrene Using 23Na NMR. 2. Effects of Solution Casting

Abstract

23Na nuclear magnetic resonance (NMR) is used to study the local environment of sodium cations in lightly sulfonated polystyrene ionomers (NaSPS). Solution casting is shown to have a significant effect on the local morphology of NaSPS. NaSPS with 1.7% styrenesulfonate groups cast from solutions of DMF or THF/water at low concentrations showed more aggregated ions than those samples cast from relatively nonpolar solvents such as THF and THF/methanol mixtures. No changes due to sample history were seen for more highly sulfonated samples (4.2% styrenesulfonate groups). The changes in morphology due to solution casting were shown to have some reversible character.

Correlation between Morphology and Mechanical Properties in Zn‐Neutralized Sulfonated Polystyrene Ionomer/Poly(ethylene glycol) Blends: Contribution of EFTEM

“…Previous works have shown that the microstructure of the ionic aggregates in SPS ionomers is strongly dependent on the sulfonation level, the polydispersity and the processing conditions. [27,28,32,33] For instance, a rapid rate of solvent evaporation in cast films of a SPS-Zn ionomer with an ionic content of about 3.4 mol-% (similar to the one used in the present study) leads to spherical aggregates of about 3 nm in diameter. [28] On the other hand, a Zn-SPS with a sulfonation degree of 5.3 mol-% prepared by compression-molding present two different shapes for the ionic aggregates: solid spheres (diameter around 5 nm) and shells or vesicles (diameter from 12 to 34 nm).…”

Radial loop and extreme vessel tortuosity in the transradial approach: Advantage of hydrophilic‐coated guidewires and catheters

“…These field gradients can be especially due to the strong electric fields posed by other Na + ions or to polymer‐affixed anions, such as—SO groups, in the vicinity. It has been established that as peaks shift to less negative values, the interactions with Na + ions become weaker 24–32. This concept can be put to use in determining whether Na + ions are isolated or exist in aggregates, although the absolute size of these aggregates cannot be derived from this method.…”

Review and critical analysis of the morphology of random ionomers across many length scales

“…23 Na NMR experiments can be used to determine quantitatively the amount of isolated ions in sodium-neutralized ionomers; these experiments are critically important since they represent the only quantitative example where the fraction of isolated ions was determined for nontransition-metal neutralized materials. In a series of papers [29,[50][51][52], Cooper and coworkers used NMR to study NaSPS in great detail. The authors found that in fully neutralized samples at $2 mol% sulfonation level, the sodium atoms were both isolated and aggregated; while at $4 mol% sulfonation level, all sodium atoms were aggregated.…”