Aqueous Solution Behavior of Poly(ethylene oxide) in Presence of Complex Ions

Poly(ethylene oxide) (PEO) in aqueous solutions has often been studied by experiment and modeling, but despite widespread use, questions about solution properties remain. Motivated by PEO’s potential to reduce CO2 emissions as a strength-building concrete additive, chain conformation was examined in solutions containing complex ions present during concrete curing. Ion-induced changes for linear 100,000 g/mol PEO were mostly unremarkable and consistent with past reports, the hydrodynamic radius by dynamic light scattering or intrinsic viscosity depressed slightly as ion concentration grows. Trends for aluminum-containing ions [at neutral and basic pH monovalent anion Al(OH)4 predominates] were different, with radius by dynamic light scattering approximately 50% larger than by intrinsic viscosity. We hypothesize weak ion-mediated coupling between hydroxyl end groups disruptable by shearing. In support, hydrodynamic radius by dynamic light scattering fell to the value by intrinsic viscosity when hydroxyl end groups were converted to methoxy end groups. The chemistry of the ion-induced chain association remains unclear.