Mixed types of phase separation

The identification of mixed types of phase separation in polymer systems causes great difficulties. Important information for phase analysis of a system with a mixed type of phase separation regions can be given by differences in the kinetics of phase separation of different nature. 

In polymer systems (as well as in low-moleoilar-weight ones), mixed types of phase separation can be observed, namely, crystalline and amorphous. In principle, for the. system crystallizing polymer+LMWL the liquidus curve can be combined with the amorphous separation region of my kind. On the state diagram, the separation regions of both the crystalline and amorphous type can either be separated spatially or superposed to each other. 

An important question in modern polymer science relates to the mechanism by which polymer-polymer solutions phase separate on crossing their critical solution temperatures or compositions (see also Volume 2 Chapter 4). Blends of two high molecular weight polymers usually produce lower critical solution temperatures, LCST s, which means that combinations of two polymers may be miscible at some lower temperature, but phase separate at a higher temperature." This is a direct result of the very small entropy of mixing of two polymers/ Two types of phase separation are known, nucleation and growth, and spinodal decomposition. 

If, as suggested by FTIR data, the situation here involves two, essentially separate, phases of OA and DPPC, one might expect a two-stage collapse in isotherms of mixed monolayers of these two components. Although it has been concluded that in the gel phase, complete separation of oleic acid and DPPC is unlikely (Lewis and Hadgraft, 1990), there is evidence from biphasic-type collapse pressures of OA/DPPC monolayers that a fair degree of phase separation does occur. It is well established that some degree of phase separation is likely in most biphasic systems, and there are several excellent review articles on this theme (e.g., Jain, 1983). 

Finally, Phase III biorefineries are the most advanced, as they use a variety of biomass feedstock to yield a mix of products (Figure 1.2). Such biorefineries employ a combination of technologies, among them are chemical and/or biological transformations, extractions, and separations. Examples for Phase III biorefineries include whole-crop biorefineries encompassing an array of transformations of feedstock (e.g., corn, or rapeseed). The most promising type of Phase HI biorefineries are... 

Some (ionic liquid + water) systems do not exhibit the usual UCST behaviour, but show a lower critical solution temperature (LCST) behaviour instead. Here, the phase separation takes place at higher temperatures and mutual solubilities increase upon cooling until a homogeneous solution is reached. Only a small change in ionic liquid structure can already change the type of phase behaviour (UCST or LCST). For example, the tetrabutyl-phos-phonium-based ionic liquid with trans 2-butenedione (fumarate) as anion shows UCST behaviour, whereas the similar ionic liquid with the cis 2-bute-nedione (maleate) shows LCST behaviour after mixing with water. ... 

When presented in this fashion, even the sample PTMO-1000-MDI-31-DCA indicates a less phase separated structure in comparison to PTMO- 00- MDI-31-DCA. Polyether polyurethane based on MDI/BD (ESTANe ), which had indicated a smaller interfacial thickness, shows a considerable amount of mixing between the two types of segments. In general, a good correlation can be found between the degree of phase separation as determined by x-ray analysis and mechanical and thermal characteristics observed earlier. 

If the forces between two different molecules are of similar type , the molecules behave as indistinguishable and they mix. Those substances in liquid state are miscible. If the forces are not of a similar type , a phase separation will happen and the liquids are called immiscible. 

Several types of information can be obtained by multinuclear solid state NMR, such as stmctural homogeneity, degree of condensation of the inorganic species, presence of mixed X-O-Y linkages in case of mixed oxide compositions, phase separation and polymerization of the organic functional groups. 

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