Coarsening, polymer blend phase separation

Conflicting results have been found for the explicit time evolution of the correlation length during isothermal phase separation. A 1/3-power law in the growth of patterns, which is characteristic for the hydrodynamically controlled Lifshitz Slyozov process, was confirmed in Ref. [99] while an exponential increase over a certain period of time was established in Ref. [21]. Nevertheless, it is evidenced that in blends comprising liquid-crystalline polymers spinodal decomposition and subsequent coarsening processes take a course similarly to isotropic liquid mixtures. 

The simulation result for the time evolution of structure factors as a function of the scattering vector q for an A/B 75/25 (v/v) binary blend is shown in Fig. 9 where time elapses in order of Fig. 9c to 9a. The structure factor S(q,t) develops a peak shortly after the onset of phase separation, and thereafter the intensity of the peak Smax increases with time while the peak position qmax shifts toward smaller values with the phase-separation time. This behavior suggests that the phase separation proceeds with evolution of periodic concentration fluctuation due to the spinodal decomposition and its coarsening processes occurring in the later stage of phase separation. These results, consistent with those observed in real polymer mixtures, indicate that the simulation model can reasonably describe the phase separation process of real systems. 

Phase separation in binary alloys, polymer blends, and fluid mixtures has been studied intensively for many years [148]. It takes place when a two-component mixture is quenched from a disordered state into a two-phase coexistence region. After such a quench, composition fluctuations are created that grow and form domain structures. In the late stages, the domain structure coarsens in time, a process that is driven by the interfacial tension coexisting phases. The growth of the characteristic length scale R t) follows a power-law behavior,... 

Figure 7.3 Transient morphologies of phase-separating polymer blends with and without nanoparticles, (a) Optical micrograph of a phase-separating deuterated polystyrene (dPS)/polybutadiene (PB) 70 30 critical mixture after coarsening for 1510 min at 25 °C [40] (b) snapshot of a Langevin dynamic simulation ofa critical (50 50) AB-mixture, with...

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