Solid-like phase

Influence factors relating to transition between the liquid phase and the solid-like phase ... 

A decrease in occupied area of the head group results in an increase in packing density of the molecules (45) exhibits only an expanded phase, (46) both a liquid and a solid-like phase, and (47) forms only a condensed film. Monolayer properties of many natural phospholipids and synthetic amphiphiles are described in the literature37 38. Especially the spreading behaviour of diacetylenic phospholipids at the gas-water interface was recently described by Hupfer 120). 

Monolayers show different gas-, liquid-, and solid-like phases. This can be observed with a film balance. The shape of phase boundaries within monolayers are determined by the competition between electrostatic repulsion of the molecular dipole moments, the van der Waals attraction, and the perimeter-minimizing line tension. 

A two (or more) component system, comprising a fibrous solid-like phase (typically ca. 1 % by weight) immobilising a much larger liquid volume. 

As described in the preceding section, our model molecule has four local minima [16]. (See Fig. 1.) As the energy is increased from the solid-like phase, trajectories begin to get out of the potential basin of PBP structure and travel around the other basins. We would like to explore how the dynamics of structural change proceeds with time. To this end, we define a simple indicator that can detect the structural transitions with high sensitivity. Let be a position vector from the octh to ith particles. Suppose a triangle plane that is expanded by two... 

Figure 4. The time series of at three typical energy regions. (a) — 15.505e (solid-like phase), (h) -13.505e (coexistence region), and (c) —11.505e (liquid-like phase). (Reproduced from Ref. 19 with permission.)...

An equally remarkable feature to whidi we shall turn now is the fact that confined fluids may sustain a certain shear stress without exhibiting structural features normally pertaining to solid-like phases that is, they do not necessarily assume any long-range periodic order. We tacitly assumed this from the very beginning of this book in our development of a thermodynamic description of cuiifiiied fluids, wliich closely resembles that appropriate for solid-like bulk phases (see Section 1) (12). 

The behavior and characteristics of confined fluids is more complex than that of bulk liquids or of simple solvated systems described in the chapters mentioned above. One must consider the complexities of the interface between confining walls and the fluid along with confinement-induced phase transitions, critical points, the stratification of the fluid near the confining walls, the idea that confined fluids may sustain certain shear stress without exhibiting structural features normally associated with solid-like phases, and... 

Let us consider a vessel with multifunctional monomers. Each monomer may react by one or more of its/functional groups. As time proceeds, there is a formation of dimers, trimers,..., polymers this is the sol. This process makes the solution more and more viscous, because of the presence of large macromolecules. The viscosity diverges, and this defines a threshold time /. For t > L, in addition to the sol, there is an infinite molecule, the gel. Thus, there appears an elastic modulus due to the presence of a solid-like phase. 

High pressure measurements on various lubricants are presented. Ultrasonic results are given and show that some of the investigated fluids change from a liquid state to a solid-like phase. Pressure viscosity results are also reported and a good correlation between ultrasonic and viscosity results is noted. Furthermore, some unstationary effects obtained on paraffinic base oils are presented and discussed. 

Due to the number of fluids investigated, results are reported in Table Il-a and Table Il-b and some typical cases are plotted in figures 1 and 2. A discontinuity in the sound velocity versus pressure curves can be observed in some lubricants (fig. 2). This discontinuity is interpreted 24 by the apparition of an amorphous phase (a solid like phase) in the sample. Due to the hydrostatic pressure, molecules are compressed and the free volume available is also reduced. Ultra sonic waves are sensitive to this evolution longitudinal waves introduced local pressure fluctuations and the speed of propagation is dependant of the density and the molecular state of the tested sample. 

All Isotherms are of Type I, being almost identical to those of N2. The uptake of Ar at the low pressure region is more gradual than that of N2, which should be attributed to the absence of the quadrupole in the Ar-ACF system. These Ar adsorption isotherms were analyzed by the DR plots. Figure 4 shows the DR plot of the Ar adsorption on CEL. The DR plot is not linear but there are three concave regions against the abscissa the DR equation does not express the Ar adsorption. Ar does not form Fig. the liquid-like adsorbed layer Ar on upon adsorption of Ar at 77 K, but should form the solid-like phase on the surface. The DA equation of n=3 may be applicable to such a system[3,27]. Figure 5 shows the DA(n-3) plots for the Ar adsorption Isotherms on ACF s at 77 K. The DA plot has three sections as well as the DR plot for the N2 adsorption Isotherm. 

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