Viscosity prediction of polyethylene glycol–dextran–water solutions used in aqueous two-phase systems

The dynamic viscosities of aqueous polyethylene glycol and dextran, and poly(ethylene glycol)–dextran–water solutions were measured at temperatures of 30, 50 and 70°C. The poly(ethylene glycol) having a relative molecular mass of 8000, and dextran samples with relative molecular masses of 37 500, 494 000, and 2 000 000 were used. A one-parameter Grunberg-like equation proposed earlier by us was used for estimating the values of viscosity of poly(ethylene glycol)–dextran–water solutions. The disposable parameter a for this temperature range was calculated as 1.81 for PEG 8000–dextran 37 500–water solutions, as 2.36 for PEG 8000–dextran 494 000–water solutions, and as 2.57 for PEG 8000–dextran 2 000 000–water solutions. It was observed that the relative errors get larger as the relative molecular mass of the dextran increases but vary between 0.00 and 9.37 in absolute value. In view of the results obtained here and before, we may claim that the proposed model works constantly well at different temperatures giving comparable values for the disposable parameter a.