Phase transition phenomenon

Crystallization is a phase transition phenomenon. Crystals grow from an aqueous protein solution when the solution is brought into supersaturation (Ataka, 1993). Supersaturation is achieved by varying the concentrations of precipitant, protein and additives, pH, temperature, and other parameters (McPherson, 1999 Ducruix and Giege, 1992 Ducruix and Giege, 1999). 

It is indeed somewhat surprising that the quantity of each phase is in some sense irrelevant to thermodynamic description of the phase-transition phenomenon. Consider, for example, a 1 kg sample of pure water in equilibrium with its own vapor at, say, the normal boiling point (T = 100°C, P = 1 atm), initially with rcvap moles of vapor and nnq moles of liquid, as shown at the left ... 

The onset of percolation and the conditions that produce this phase-transition phenomenon have been of considerable interest to many disciplines of science. The classical studies have focused on immobile ingredients in a system that increase in concentration by randomly adding to the collection of particles. It is possible to estimate the conditions leading to the onset of percolation under these circumstances. When the ingredients are in motion, this estimation is far more difficult. It is an obvious challenge that was tackled using cellular automata. 

As discussed in the previous section, the molecular interactions rule the mam)-scopic size and shape of gels. Since these interactions are functions of temperature, polymer concentration, solvent composition (if a mixture of solvents is used), and pH and salt concentration (for geb capable erf ionization), the volume phase transition can be induced by controlling one or some of these parameters. Before the phase transition was found in gels, various researchers had developed gels that change their degree of swelling when a stimulus b applied to them. This article, however, will describe only the systems that use the phase transition phenomenon. 

Abstract In order to tailor hydrogels for the application as actuator-sensor microsystems based on the responsive behaviour of smart gels, a general strategy has to be developed. Since the phase transition phenomenon of hydrogels is theoretically well understood advanced materials based on the predictions can be prepared. The requirements for applying hydrogels can be summarized as follows ... 

Although micellization is not strictly speaking a phase transition phenomenon, nucleation and growth can also be used here. The micelles are then seen as droplets that can only grow up to limited size and wiU form a new continuous body (new phase). The next section reviews an example of such an approach. 

In this article, we introduce a recently developed ultrasonic spectroscopy method and review its application to polymeric studies. First, the principle of this ultrasonic spectroscopy is explained including the instruments and data analysis methods. Then, actual application of this measuring system is described for the characterization of solid polymers and the observation of phase transition phenomenon in liquid crystals and ferroelectric (VDF/TrFE) copolymer. Finally, the extension of this system to two-dimensional measuring and the application to non-destructive testing of CFRP (carbon fiber reinforced plastics) are discussed. 

On the other hand. Fig. 20 shows the temperature dependence of the velocity at different frequencies of 1,3,5, and 7MHz, revealing a critical lowering phenomenon around the Curie temperature, which is characteristic of the ferroelectric phase transition phenomenon. The sound velocity at higher frequencies seems to show this lowering phenomenon at a lower temperature range compared with that at lower frequencies. 

Figure 1.1 Curves showing phase transition phenomenon, (a) Lower critical solution temperatnre (LCST) and (h) npper critical solution temperature (UCST) phase transition behaviors of thermo-responsive polymers in solution.

The lack of a sharp phase transition phenomenon in the case of PSEG(l/3) shown in Figure 5a may be attributable to hydrolysis during the measurement. 

Polymer gels are different from normal solids and liquids and show various characteristics and behaviors. It is known, for example, that the water in gels exists in several different forms non-freezable water even at very low temperature that exists close to the network and has a strong interaction with the network bound water that freezes at —10 to —20°C and free water that has the same properties as normal water. There is also the phase transition phenomenon in which a gel is nonlinear. Phase transitions caused by solvent composition, temperature changes, pH... 

There are several notable phenomena in the phase transition of gels in mixed solvents. One of them is the reentrant phase transition phenomenon. This is the phenomenon in which a successive change, swelling-shrinking-swelling, occurs as a function of solvent composition. Although... 

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