The miscibility of dextran (Dx) with poly(ethylene glycol) (PEG) was investigated in dilute aqueous solutions by viscometry. Homopolymers of Dx and PEG and their blends with Dx/PEG ratios of 10/90, 25/75, 50/50, 75/25, and 90/10 were studied at 25, 30, 35, 40, and 45 degrees C in bidistilled and deionized water. Starting with the classical Huggins equation, the results of the viscosity behavior of each parent polymer and their blends were interpreted in terms of miscibility parameters, Delta k, Delta b, alpha, beta, Delta B, and mu. On the basis of the sign convention involved in these criteria, miscibility between Dx and PEG was found to increase with the weight fraction of PEG in the blend composition and temperature. The fourier transform infrared (FTIR) analysis is also used to investigate the miscibility of the polymer pairs. The existence of specific interactions between Dx and PEG was demonstrated by FTIR spectroscopy. (c) 2006 Wiley Periodicals, Inc.