Abstract
The viscoelasticity of poly(ethylene glycol) (PEG) in aqueous solutions with different concentrations of potassium sulfate (K2SO4) was studied by quartz crystal microbalance with dissipation (QCM-D), after coating a rigid supported lipid bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine on the silicon oxide substrate. The obtained viscoelastic properties of PEG in K2SO4 solutions agree well with the Zimm model predictions for linear polymer chains. With increasing K2SO4 concentration, the excluded volume exponent ν of PEG decreased from 0.565 in water to 0.55 in 0.19 mol/L K2SO4, and 0.50 in 0.43 mol/L K2SO4. The solvent quality gradually worsened for PEG with increasing K2SO4 concentration, which was verified by decreases in the polymer intrinsic viscosity and the corresponding Mark–Houwink exponent. The high-frequency characteristic of QCM-D makes it possible to directly study the viscoelasticity of polymer solutions in a low-viscosity solvent, which is complementary to conventional rheometers working at low frequency. Viscoelasticity of PEG in aqueous solutions containing different concentrations of K2SO4 was studied by QCM-D, after coating a rigid supported lipid bilayer on the silicon oxide substrate. The obtained viscoelastic properties of PEG in K2SO4 solutions agree well with the Zimm model predictions for linear polymer chains. The gradual worsening of solvent quality by adding K2SO4 to aqueous PEG solutions is demonstrated by the obtained excluded volume exponents via QCM-D and the conventional intrinsic viscosity measurements.
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