Ice nucleation and supercooling behavior of polymer aqueous solutions.

We determined the homogeneous nucleation temperature depression, DeltaT(f,hom), the equilibrium melting point depression, DeltaT(m), and the value lambda, which can be obtained from the linear relationship DeltaT(f,hom)=lambdaDeltaT(m), for aqueous solutions of PEG (200-20,000 g mol(-1)), PVP (10,000, 35,000, 40,000 g mol(-1)), and dextran (10,000 g mol(-1)) in the concentration range 0-40 wt% using the emulsion method. The molecular weight dependence of T(f,hom), T(m), and lambda in PEG aqueous solutions was found to change in the vicinity of Mw 600-1540 at all concentrations. In addition, it was confirmed that for all of the polymers studied, there was a good linear relationship between lambda and the logarithmic value of the self-diffusion coefficient D(0) of the solute molecule. These results indicate that the parameters that describe non-equilibrium freezing, such as T(f,hom) and lambda, are dependent on solution properties such as viscosity and self-diffusion of solute molecules.