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Shift in Polymer Blend Phase-Separation Temperature in Shear Flow



Jack F. Douglas


Recent experimentalstudiesof polymer blendsin simple shear flow have indicated large *Shih of the apparent phase-separation temperature. These shifts are examined within the context of a nonequilibrium hydrodynamic theory of phase separation developed by Onuki and Kawasaki. A mean-field version of the hydrodynamic theory indicates that no true shift of the critical temperature Tc, should be observed in high molecular weight polymer blend melts. However, the hydrodynamic theory indicates a large apparent shift )in the critical temperature parallel to the flow direction is proportional to shear rate (y) e(8/15). if the scattering data naively fit to the Ornstein- Zernike function. This spurious shift should not be observed in scattering data along the normal to flow direction. These predictions accord qualitatively with experiments on sheared melt blends by Nakatani et al. The apparent shift of Tc, in high molecular weight polymer melt blends. is coincidentally similar to the true shift of Tc, observed in small-molecule binary mixtures is obtained from mode-coupling renormalization group theory. It is argued that a true shift of Tc, should be observed in sufficiently diluted polymer blends in low molecular weight solvents because of a crossover from mean-field critical behavior upon dilution.
25 (1992)
ACS Reprint May 1st, 2002


polymer blend, phase separation, rheology


Douglas, J. (2002), Shift in Polymer Blend Phase-Separation Temperature in Shear Flow, Macromolecules, [online], (Accessed April 16, 2024)
Created May 1, 2002, Updated February 19, 2017