Industrial & Engineering Chemistry Research · 2010 · 16 citations · 57 references
Natural SciencesChemistryMaterials SciencePhysical ChemistryPolymer ChemistryPolymer MaterialsPolymer CharacterizationPolymer Phase BehaviorPolymer Physical ChemistryPolymer PhysicsPolymer StabilityPolymer ThermodynamicsAqueous Biphasic SystemsPartitioningPolymer Concentration EffectsPolymer Molecular CharacteristicsPolymer Solution ThermodynamicsTemperature EffectsTemperature Effects On PartitioningThermal Properties
In common with many poly(ethylene glycol)s (PEGs), a poly(ethylene oxide)−poly(propylene oxide) random copolymer (EO−PO, with EO/PO = 1:1.3) of molecular weight 3320 g·mol −1, known as Sunbright-3320 (SB-3320), can be salted out of aqueous solution using kosmotropic salts such as (NH 4 ) 2 SO 4 to form aqueous biphasic systems (ABSs) comprising upper polymer-rich and lower salt-rich aqueous phases. The effects of temperature on these liquid/liquid ABSs and related solid/liquid resin-based systems, where one end of the polymer has been covalently attached to a solid support, have been studied. Distribution ratios of NH 4 99 TcO 4 were determined radiometrically at various polymer and salt concentrations and temperatures. SB-3320-grafted poly(styrene) resins exhibit opposite effects of variable-temperature partitioning compared to the SB-3320-based ABS. However, the results are complicated because of the conformational changes that are possible for the SB-3320 polymer. Enthalpy and entropy changes were found to be temperature-dependent. The differences observed between the distribution of 99 TcO 4 − in EO−PO-based systems versus PEG-based systems can be attributed to the lower cloud point temperatures and probable conformational changes for the EO−PO systems.
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Keith E. Gutowski, G.A. Broker, Heather D. Willauer et al. · Journal of the American Chemical Society · 2003 · 1K citations