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RESEARCH PRODUCT

Ionomers in solution: 1. Viscometric and chromatographic studies in cononsolvent and cosolvent mixtures

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Abstract The viscosity and elution behaviour of polystyrene sulfonate ionomers with varying ionic content has been studied in the pure solvents chloroform (CHL), tetrahydrofuran (THF), dioxan (DIO), ethyl acetate (EA) and dimethylformamide (DMF) as well as in their cononsolvent mixtures CHL/THF (50:50), DIO/CHL (75:25) and in the cosolvent mixture EA/DMF (50:50). In the pure solvents with low dielectric constant the reduced viscosities of ionomers are lower at low concentrations and higher at moderate ones than the respective viscosities of the polystyrene precursor. These results can be explained by formation of intramolecular and intermolecular associations. Moreover, differences in viscosity with the precursor are greater the higher the ionic content of the ionomer, and they are also enhanced in the cononsolvent mixtures. In contrast, ionomers with the highest ionic content behave in DMF as polyelectrolytes. This trend is weakened in the presence of EA, which seems to interact strongly with ionomers; the higher their ionic content the greater is this interaction. Moreover, whereas the ionic part of ionomer is preferentially solvated by EA, the hydrocarbonated part is solvated by DMF. Secondary exclusion mechanisms invert the order in elution volumes of ionomers when changing the eluent and/or the chromatographic gel.