Phase Separation in Crystalline Polymer Blends

When further heated up to 200 C, all the initially clear samples became turbid in succession, but the remixing did not occur when these samples were cooled due to kinetic effects. Careful microscopic observations revealed that the turbidity was caused by the formation of a phase-separated structure. These results suggest that the PES-C-PEO blends display LCST behavior, which means that there is a negative enthalpic contribution of mixing. 

From the crystallinity of PEO as a function of blend composition, a dramatic decrease in crystallinity is observed when the content of PES-C is more than 20%, indicating a pronounced 

All these results clearly show that PES-C-PEO blends are miscible and exhibit an LCST behavior. However, as shown above, different thermal behaviors are shown by the miscible blends of PES-C and PEO, depending on the blend composition. Blends with different compositions display different changes in thermal properties when phase separation occurs. Therefore, the investigation of phase separation should be performed in the light of the blend compositions. The studies of phase separation process are discussed in detail as below. 

For the 50 50 PES-C-PEO blend, an amorphous and homogeneous mixture was obtained after quenching from 80 to -70 °C in terms of the 

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Phase Field Modeling on Polymer Crystallization and Phase Separation in Crystalline Polymer Blends... 

Also dewetting and phase separation using crystalline polymers, such as poly(e-caprolactone) (PCL), has been described recently. Fu et al. [131] recently found that in PS/PCL blends a two-layer structure with PS at the upper layer and PCL at the bottom layer was formed during spin coating. The authors varied the solution concentration and as a consequence the thickness of the films formed and found that the crystallization is dependent of the final film thickness. So that, different kinds of crystal morphologies, such as fmger-like, dendritic, and spherulitic-like, could be obtained at the bottom PCL layer. 

Because the phases are physically separated in the melt, the theory concerning the crystallization behavior as discussed in Parts 3.4.3 (matrix crystallization) and 3.4.4 (dispersed droplet crystallization) can be combined to understand the crystallization and melting behavior of most crystalline/ crystalline polymer blends. In general, both crystal-lizable phases crystallize separately around then-characteristic bulk T-value (as long as the minor phase is not dispersed into very fine droplets). The T-values can be somewhat shifted due to... 

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