Solute segregation regimes

Hashimoto T., Shibayama M., and Kawai H., Ordered structure in block copolymer solution. 4. Scaling rules on size of fluctuations with block molecular weight, concentration temperature in segregation and homogeneous regimes. Macromolecules, 16, 1093, 1983. 

When solute atoms rather than tracer isotope atoms diffuse in the B regime, further analysis is necessary. Solute atoms may be expected to segregate in the... 

In a blend of immiscible homopolymers, macrophase separation is favoured on decreasing the temperature in a blend with an upper critical solution temperature (UCST) or on increasing the temperature in a blend with a lower critical solution temperature (LCST). Addition of a block copolymer leads to competition between this macrophase separation and microphase separation of the copolymer. From a practical viewpoint, addition of a block copolymer can be used to suppress phase separation or to compatibilize the homopolymers. Indeed, this is one of the main applications of block copolymers. The compatibilization results from the reduction of interfacial tension that accompanies the segregation of block copolymers to the interface. From a more fundamental viewpoint, the competing effects of macrophase and microphase separation lead to a rich critical phenomenology. In addition to the ordinary critical points of macrophase separation, tricritical points exist where critical lines for the ternary system meet. A Lifshitz point is defined along the line of critical transitions, at the crossover between regimes of macrophase separation and microphase separation. This critical behaviour is discussed in more depth in Chapter 6. 

In the case of DNA collapse in a solution of neutral polymer incompatible with DNA molecules, two main effects have to be taken into account. The first effect is the osmotic pressure of the counterions on the DNA coil. The second effect is connected with the difference in polymer concentration inside and outside the DNA coil. It was found that the concentration of neutral polymer within the effective volume of DNA is always lower than that in external solution. This difference could be negligible in the case of good compatibility observed at low polymer concentration. In this case the polymer molecules practically freely penetrate inside the DNA coil, so that the water/polymer composition inside the DNA coil is the same as the composition in the external solution. The second regime is the regime of practically perfect segregation between the DNA chain and the polymer. The polymer segregates from the DNA coil and imposes additional osmotic pressure,... 

Figure 11 SCC penetration as a function of potential for caibon steel and low-alloy Cr-Mo steel tested in hot NaOH solution, showing a cracking regime at higher potential induced by P segregation to grain boundaries [66]. See also Figure 22.

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