Phase diagram, polymer-water

Recently, new ordered mesoporous silicas have also been synthesized by using self-organization of amphiphilic molecules, surfactants and polymers either in acidic or basic condition. A schematic phase diagram of water-surfactant is shown in the figure. 

YOU Young, T.-H., Cheng, L.-P., You, W.-M., and Chen, L.-Y., Prediction of EVAL membrane morphologies using the phase diagram of water-DMSO-EVAL at different temperatures. Polymer, 40, 2189, 1999. 

Figure 22.2. Phase diagram of water at low temperature. Note the no-man s-land between and Tx. This region can only be accessed by restricting the crystallization. An example of such a system is water in a nanotube. Note the extended HDA/LDA first-order phase transition line into the no-man s-land region which ends in a critical point denoted by the dot at the end of the Une. At atmospheric pressure if one decreases the tempemture, then the region beyond the eritieal point is accessed. The figure is reproduced from the thesis of Dr. Pradeep Kumar, http //polymer.bu.edu/ hes/water/thesis-kumar.pdf.

In order to explain the experimental phase diagrams of water-soluble polymers, a number of semiempirical approaches that assume the concentrational dependence of the Flory-Huggins solubility parameter were developed. " " Hie two-state models, which involve equilibtium coexistence of two interconvertible (solvophilic and solvophobic) states of the monomer units, as well as the n-duster model, which assumes temperature-dependent inversion of the higher order virial coeffident, allow to rationalize the apparent concentrational dependence of the solubility parameter in aqueous solutions of water-soluble polymers. 

POL Polyakov, V.I., Grinberg, V.Ya., and Tolstoguzov, V.B., Application of phase-volume-ratio method for determining the phase diagram of water-casein-soybean globulins system, Polym. Bull, 2, 757,1980. 

Polyakov, V. L, Grinberg, V. Ya, Tolstoguzov, V. B. (1980). Application of Phase-Volume Ratio Method for Determining the Phase Diagram of Water-Casein-Soybean Globulins System. Polymer Bulletin, 2,160-161. 

The basis for the separation is that when two polymers, or a polymer and certain salts, are mixed together in water, they are incompatible, leading to the formation of two immiscible but predominantly aqueous phases, each rich in only one of the two components [Albertsson, op. cit. Kula, in Cooney and Humphrey (eds.), op. cit., pp. 451 71]. A phase diagram for a polyethylene glycol (PEG)-Dextran, two-phase system is shown in Fig. 22-85. Proteins are known to distribute unevenly between these phases. This uneven distribution can be used for the selective concentration and partial purification of the products. Partitioning between the two phases is controlled by the polymer molecular weight and concentration, protein net charge and... 

The hydrophobic interaction results in the existence of a lower critical solution temperature and in the striking result that raising the temperature reduces the solubility, as can be seen in liquid-liquid phase diagrams (see Figure 5.2a). In general, the solution behaviour of water-soluble polymers... 

The system polyethylene glycol (PEG)-dextran-water is still the most used and best-studied aqueous polymer two-phase system. A phase diagram for a typical two-phase system is shown in Fig. 10.12 for the PEG-dextran system. Both polymers are separately miscible with water in all proportions. As the polymer concentration increases, phase separation occurs, with the... 

The influence of a cream containing 20% glycerin and its vehicle on skin barrier properties has been investigated. Recent studies have shown that polymers offer several advantages and can be used in skin care products. Phase diagrams were determined for lactic and isohexanoic hydroxy acids as well as salicylic acid with water, a nonionic surfactant and a paraffinic oil, to outline the influence of hydroxy acids on the structure in a model for a skin lotion. The results showed the influence of the acid to be similar to that of the oil but that the difference in chain length between the two alpha acids had only insignificant influence. The results are discussed from two aspects the structures involved in the lotion as applied, and the action of the lotion residue on the skin after the evaporation of the water. 

Diphasic liquid systems used in CCC may have a wide variety of polarities. The most polar systems are the ATPS made by two aqueous-liquid phases, one containing a polymer, for example, polyethylene glycol (PEG), the other one being a salt solution, for example, sodium hydrogen phosphate. The less polar systems do not contain water there can be two-solvent systems, such as heptane/acetonitrile or dimethylsulfoxide/hexane systems or mixtures of three or more solvents. Intermediate polarity systems are countless since any proportion of three or more solvents can be mixed. Ternary phase diagrams are used when three solvents are mixed together. 

FIG. 8.13 Two representations of a portion of the phase diagram for the water-benzene-potassium oleate-pentanol system. The unshaded regions represent homogenous solutions, (a) Redrawn, with permission, from S. Friberg and I. Burasczeska, Prog. Colloid Polym. Sci., 63, 1 (1978). (b) Redrawn, with permission, from C. U. Herrmann, U. Wurz, and M. Kahlweit, In Solution Chemistry of Surfactants, Vols. 1 and 2 (K. L. Mittal, Ed.), Plenum, New York, 1979. 

Besides the l.c. phases, the phase diagram of the p-l.c./water is very similar to the diagram of the m-l.c./water. The broad miscibility gap of the polymer/water system shows a lower critical consolute point, which is shifted to lower concentrations (3.2% of polymer). This is consistent with experiments and theory on the position of miscibility gaps in polymer solutions112). 

Figure 3.12 Membrane formation in water-precipitation membranes was first rationalized as a path through the three-component phase diagram from the initial polymer casting solution (A) to the final membrane (D) [24]...

FIGURE 7.32. Phase diagram of PMOXA-b-PDMS-b-PMOXA in water and Cryo-TEM image of the lamellar phase formed at x = 50. x = polymer fraction in water in % w/w La = lamellar liquid crystalline phase. 

First, it is necessary to establish the phase diagram of the aqueous two-phase system formed by water and two water-soluble polymers. Second, a method must be established for calculating the distribution coefficient of a biomolecule that partitions between the two aqueous phases. A simple molecular-thermodynamic description is provided by the osmotic virial... 

This polymer is spun from a solution in pure (100%) sulphuric acid. A typical, but too simple phase diagram for the PpPTA-sulphuric acid/water system is shown in Fig. 19.24 (also shown as Fig. 16.27). It shows that the solution is solid at sulphuric acid/water ratio smaller than approximately 0.95 liquid solutions are obtained at high sulphuric acid contents at low polymer concentrations isotropic solutions are obtained whereas at higher polymer concentrations the solutions are anisotropic. It is clear that for solution spinning almost pure sulphuric acid or even oleum (i.e. H2SO4... 

FIG. 19.24 A typical phase diagram for poly (p-phenylene terephthalamide) showing percentage polymer plotted against percentage sulphuric acid in water >100% sulphuric acid is obtained by adding S03 (this is called oleum). After Dobb (1985). 

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