Determination of both the binodal and the spinodal curves in polymer blends by shear rheology

The thermorheological complexity at low frequencies in polymer blends near macrophase separation is quantitatively accounted for. The behaviour of both storage, G ′, and loss, G ′′, moduli at low frequencies as the temperature, T , approaches phase separation is due to the critical concentration fluctuations in the one-phase region. The temperature at maximum slope of the G ′ vs. T dependence at low frequencies is identified with the cloud point curve, whereas a plot of [( G ′′) 2 /( G ′ T )] 2/3 vs. 1/ T leads to the identification of the spinodal temperature.