Influence of Rheology on Thermodynamics

Rapid change of temperature to Tg causes phase separation by the mechanism known as spinodal decomposition (SD), which is characterized by the presence of two interpenetrating continuous phases that coarsen with time. Thus, the morphology within the metastable region is time dependent and in consequence so is the rheological response. Theoretically, instantaneous SD formation of interpenetrated structures causes the linear viscoelastic functions to go to infinity ]216, 217]  

For steady-state shear flow of a spinodal blend, Onuki [218-220] postulated that the shear stress is the same in two phase-separating liquids, which leads to the effective viscosity and the first normal stress difference as  

The dependence implies that at S D or phase inversion the viscosity ratio equals the volume fraction ratio ofthe separated phases A = = 2/ 1 - this assumption 

Sharma and Clarke [221] suggested the use of an isochronal ( o = 1 rad s ) dynamic temperature scan for detecting the critical temperature of miscibility. A plot of either log G or log(tand) versus T for deuterated-PS (PSD)/PPE blend had a slope that changed at LCST = 104 °C. The method also provided information on the range of the metastable zone of temperatures. A similar conclusion was draw from the dynamic data at =0.1 rads [197]. 

Mani et al. [210, 226] have measured the fluorescence intensity during a temperature scan (at 1 K min ) of PS/PVME blends while shearing in a cone-and-plate 

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