Anomalous Phase Separation Dynamics under Asymmetric Viscoelastic Effect: Where Fluidic and Elastic Properties Meet

Manipulating the kinetics and mechanism of phase separation in dynamically asymmetric LCST blends by nanoparticles

The addition of nanoparticles in dynamically asymmetric LCST blends is used to induce the preferred phase-separating morphology by tuning the dynamic asymmetry, and to control the kinetics of phase separation by slowing down (or even arresting) the domain growth.

Does dynamic vulcanization induce phase separation?

Immiscible and miscible blends of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) were subjected to dynamic vulcanization to investigate the effect of crosslinking on phase separation. As a result of different processability, mixing torque behavior of miscible and immiscible blends was significantly different from one another. Scanning electron microscopy (SEM) was used to investigate the morphology of the system. After dynamic vulcanization, submicron ACM droplets were observed in the samples near the binodal curve of the system under mixing conditions. Small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) analysis were used to investigate the effect of dynamic vulcanization on the lamellar structure of the system. It was shown that for samples near the boundary of phase separation, increasing the crosslink density led to a decrease in the lamellar long period (L) as a sign of increment of crosslink density induced phase decomposition. Effects of shear rate on the final morphology of the system were investigated by changing the mixing temperature and by comparing the results of dynamic vulcanization at one phase and two phase regions.

Hierarchical coarsening in the late stage of viscoelastic phase separation

Coarsening is a general phenomenon in phase separating mixtures. In this study, we report a hierarchical coarsening at different length scales. Dispersed domains grew by direct combination of two/three small ones while some small domains can survive for a long time. The small angle laser light scattering showed that the scattered intensity exhibited multiple "decay-growth" transitions in the coarsening process. The evolution of the main peak gave a characteristic power law index of about -3/4, which is much faster than the -1/3 relationship from the traditional theories. We propose that relaxation and hydrodynamic flow play important roles in this process.