Abstract
The rheological behavior of miscible blends was studied through oscillatory shear measurements. Two miscible blends were selected to compare with athermal blending cases, i.e. the hydrogen bonding poly(4-vinyl phenol)/poly(ethylene oxide) (PVPh/PEO) blend and the weakly interacting polystyrene/poly(2,6-dimethyl-1,4-phenylene oxide) (PS/PPO) blend. The homopolymers and the blends were characterized over a wide experimental window using the time–temperature superposition principle.The horizontal shift factor, aT, does not vary appreciably with composition for PS/PPO, whereas a strong compositional dependence is observed for the PVPh/PEO blends. Additions of up to 30wt% of PEO to PVPh produce only minor changes in the value of rubber plateau modulus (GN0), while GN0 increases steadily after this concentration. The GN0 values follow athermal blending models [J. Polym. Sci., Part B: Polym. Phys. 25 (1987) 2511; J. Polym. Sci., Part B: Polym. Phys. 26 (1988) 2329] in the case of PS/PPO but not of PVPh/PEO. Values of η0b for PVPh/PEO blends were estimated from weighed relaxation spectra. The three measured parameters, aT, GN0 and η0 show a turning point around 20–30wt% of PEO, which corresponds to a 41–54mol% of PEO, in correlation with the previously reported observation of a maximum in the deformation-induced uniaxial orientation behavior of PEO component near this composition [Macromolecules 32 (1999) 8509].
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