Phase separation macroscopic

Colloidal suspensions are, per definition, mixtures of mesoscopic particles and atomic liquids. What happens if there are several different species of particles mixed in the solvent One can invent several different sorts of mixtures small and large particles, differently charged ones, short and long rods, spheres and rods, and many more. Let us look into the literature. One important question when dealing with systems with several components is whether the species can be mixed or whether there exists a miscibility gap where the components macroscopically phase-separate. 

Vesicles [10, 11] these aggregates of insoluble natural or artificial amphiphiles in water can have various shapes (spherical, cylindrical). Depending on the preparation conditions, small unilamellar or large multilamellar vesicles can be produced. The structures meet the self-organization criterion, because they are, albeit on a long time scale, dynamic and not in thermodynamic equilibrium, which would in many cases be a macroscopically phase separated lamellar phase. 

Fig. 67 Schematic of phase behaviour for blend of novolac epoxy resin with nearly symmetric poly(methyl acrylate-co-glycidylmelhacrylate)-0-polyisoprene. Ordered L can be swollen with up to about 30% of resin before macroscopic phase separation occurs, producing heterogeneous morphologies containing various amounts of L, C, worm-like micelles and pristine epoxy. At lower concentrations, disordered worm-like micelles transform into vesicles in dilute limit. According to [201]. Copyright 2003 Wiley...

An A-B diblock copolymer is a polymer consisting of a sequence of A-type monomers chemically joined to a sequence of B-type monomers. Even a small amount of incompatibility (difference in interactions) between monomers A and monomers B can induce phase transitions. However, A-homopolymer and B-homopolymer are chemically joined in a diblock therefore a system of diblocks cannot undergo a macroscopic phase separation. Instead a number of order-disorder phase transitions take place in the system between the isotropic phase and spatially ordered phases in which A-rich and B-rich domains, of the size of a diblock copolymer, are periodically arranged in lamellar, hexagonal, body-centered cubic (bcc), and the double gyroid structures. The covalent bond joining the blocks rests at the interface between A-rich and B-rich domains. 

In the previous sections, we described the overall features of the heat-induced phase transition of neutral polymers in water and placed the phenomenon within the context of the general understanding of the temperature dependence of polymer solutions. We emphasised one of the characteristic features of thermally responsive polymers in water, namely their increased hydropho-bicity at elevated temperature, which can, in turn, cause coagulation and macroscopic phase separation. We noted also, that in order to circumvent this macroscopic event, polymer chemists have devised a number of routes to enhance the colloidal stability of neutral globules at elevated temperature by adjusting the properties of the particle-water interface. 

When polymer solutions encounter situations for which the thermodynamic quality of the solvent becomes poor, individual chains undergo a coil-to-globule collapse, the globules associate immediately, and macroscopic phase separation seems unavoidable. However, it has been reported that a number of polymers in water or in organic solvents form equilibrium globules, i.e. single-chain globules that remain in solution without immediate association and precipitation. 

Partial vitrification may affect kinetic processes during the coil-globule transition. Thus, at very high dilution, macroscopic phase separation well above the LCST might be stopped by partial vitrification of the polymer-rich phase. At this point we can only speculate whether vitrification interferes with the coil-globule transition or not. This problem is open for discussion and needs experimental confirmation. 

When sufficient amounts of hydrocarbon chains are mixed with water, macroscopic phase separation takes place. The saturation value of hydrocarbon... 

Before macroscopic phase separation occurs, soluble complexes are observed in solution. 

The scattered intensity increases with increasing temperature as shown in Fig. 10. The scattered intensity diverges at the spinodal temperature, Ts in this particular case Ts = ca. 34.6 °C. Experimentally such a divergence cannot be expected because a macroscopic phase separation occurs and the scattered intensity remains finite. It is worthy to note that the difference in the scattered intensities between at 34.6 °C and at 35.0 °C clearly indicates that the system undergoes a transition. The critical phenomena of the volume phase transition of non-ionic gels with respect to temperature will be discussed in Sect 5.4. 

We synthesized [13] IPNs composed of polyethylene oxide) (PEO) (polymer A) and poly(N-acryloylpyrrolidine) (PAPy) (polymer B). The IPN was synthesized by simultaneous crosslinked polymerization of APy and PEO. The overall reaction scheme for IPN synthesis by radical polymerization for APy (polymer A) and addition polymerization for PEO (polymer B) is shown in Fig. 3. This pair shows simple coacervation behavior in water. The IPN is constructed from PEO and PAPy networks as shown in Fig. 4. Chemically independent networks of polymer A and polymer B are interlocked and macroscopic phase separation in water swollen states is avoided. 

The above discussion clearly shows that the increase of anionic copolymer concentration or the strength of chain interaction can lead to a transition from intrachain contraction to interchain association. It can result in a mesoglobular phase in which a limited number of copolymer chains are associated together to form polymeric colloidal particles stable between microscopic single-chain globular phase and macroscopic phase separation (precipitation). It is not a surprise to see the formation of such stable mesoglob-... 

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