Polymer-water systems, phase

A second important aspect is the structure of the l.c. phases. At low concentrations the polymer/water system exhibits in analogy to the monomer/water system a hexagonal phase, showing the typical fan like texture (Fig. 48). Additionally at higher concentrations a lamellar phase exists, which is separated from the hexagonal phase by a cubic phase of small extent (black area in Fig. 47). With this finding, the... 

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). 

Karlstrom, G. Carlsson, A. Lindman, B., "Phase Diagrams of Nonionic Polymer-Water Systems. Experimental and Theoretical Studies of the Effects of Surfactants and Other Cosolutes," J. Phys. Chem., 94, 5005 (1990). 

State diagrams of polymer/water systems of which the polymer is water sensitive essentially seem to be of the eutectic type known from low molecular binary systems but including some peculiarities caused by non-equilibrium phenomena and incomplete phase transitions. The... 

Karlstrom G, Carlsson A, Lindman B (1990) Phase diagrams of nonionic polymer -water systems. Experimental and theoretical studies of the effects of surfactants and other cosolutes. J Phys Chem 94 5005-5015... 

It can be noticed from Figure 11.4 that the mutual solubilities of ionic liquids and water are not symmetric. Generally, a much higher mole fraction of water is present in the ionic liquid phase than ionic liquid present in the water phase at the same temperature. The UCST is thus found at very low fractions of the ionic liquid. This asymmetry is also observed in (polymer + water) systems. Therefore, there are analogies between the phase diagrams of ionic liquid solutions and polymeric ones, although this may be due to different mechanisms. 

There is much less investigations devoted to the two-phase tripotassium citrate + polymer + water systems than to those with trisodimn citrate or triammonium citrate. Jayapal et al. [216] considered the hquid-liquid equihbrium in systems with PEG 2000 at 25, 35 and 45 °C and Zafarami-Moattar and Hamidi [210] with PEG 6000 at 25, 30 and 35 °C. The effect of temperature on the phase equilibrium of the aqueous two-phase poly (polythene glycol)+tripotassium citrate system was studied by Zafarami-Moattar et al. [217]. The phase compositions and densities in... 

The hydrogenation in a liquid-liquid system with ionic liquids as the catalyst phase was also applied to the hydrogenation of polymers. The first studies were presented by the group of Rosso et al. [91], who investigated the rhodium-catalyzed hydrogenation of polybutadiene (PBD), nitrile-butadiene rubber (NBR) and styrene-butadiene rubber (SBR) in a [BMIM][BF4]/toluene and a [BMIM][BF4]/tolu-ene/water system. The activity of the catalyst followed the trend PBD>NBR> SBR, which is the same order as the solubility of the polymers in the ionic liquid. The values in percentage total hydrogenation after 4 h reaction time were 94% for PBD and 43% for NBR, and after a reaction time of 3 h was 19% for SBR. 

The chemical potential of the polymer is affected by "impurities" such as solvents or copolymerized units. For an equilibrium condition in the presence of water as the diluent, the melting temperature of starch (Tm) would be lower because p in the presence of diluent is less than pi). For the starch-water system at equilibrium, the difference between the chemical potentials of the crystalline phase and the phase in the standard state (pure polymer at the same temperature and pressure) must be equal to the decrease in chemical potential of the polymer unit in solution relative to the same standard state (Flory, 1953). By considering the free energy of fusion per repeating unit and volume fraction of water (diluent), the... 

New pH/temperature-sensitive polymer systems with transitions resulting from both polymer-polymer and polymer-water interactions have been demonstrated and their pH/temperature-induced phase transition has been investigated. Intra/intermolecular interactions via hydrogen bond play an important role in determining the phase transition. By manipulating the... 

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... 

Kenawy 64) immobilized ammonium and phosphonium peripheral functionalized dendritic branches on a montmorillonite supported chloromethylstyrene/methyl methacrylate copolymer (74-75). These polymer/montmorillonite-supported dendrimers were used as phase transfer catalysts (PTC) for the nucleophilic substitution reaction between -butyl bromide and thiocyanate, cyanide, and nitrite anions in a toluene or a benzene/water system. These PT catalysts could be recycled by filtration of the functionalized montmorillonite from the reaction mixture. Generally,... 

In their test system, the researchers used the ionic liquid l-butyl-3-methylimidazol-ium hexafluorophosphate (bmim)(PF6), which is stable in the presence of oxygen and water, with naphthalene as a low-volatility model solute. Spectroscopic analysis revealed quantitative recovery of the solute in the supercritical CO2 extract with no contamination from the ionic liquid. They found that CO2 is highly soluble in (bmim)(PF6) reaching a mole fraction of 0.6 at 8 MPa, yet the two phases are not completely miscible. The phase behavior of the ionic liquid-C02 system resembles that of a cross-linked polymer-solvent system (Moerkerke et al., 1998), even though... 

Thus, isolation of oxoammonium salts on insoluble, cross-linked polymer supports was investigated along with their implementation in polymer-assisted solution-phase synthesis.23 These isolated oxoammonium salts could be employed in a water-free system to generate highly reactive oxidation agents without the overoxidation problems normally seen in the presence of water. 

Upon addition of certain polymers such as polyethylene glycol (PEG) and dextran or salt to water, a phase boundary forms even though the system consists of only one solvent, water. When a mixture of biomolecules such as a fermentation broth or a solution of lysed cells is added to such a system, each type of biomolecule partitions uniquely between the two phases, achieving separation (Kula, 1979,1990 ... 

These variations between woods reflect differences in microscopic structure and chemical organization of the material, for phase geometry can be as important as molecular structure in determining the properties of both natural and synthetic multiphase systems (31). Therefore, it is clear that the mechanical behavior of the wood-water system cannot be explained entirely at the molecular level or as interaction of macromolecules with solvent. Nevertheless, the general trends observed do follow general principles of solvent-polymer interaction and can be so explained. 

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