Phase transitions temperature dependence

The maximum difference in phase separation temperature was observed at a very small azobenzene content of 2.7 mol%. Below and above this content, the phase separation was not affected by photoirradiation. This fact indicates that the phase transition temperature depends on a subtle balance between the polymer s ability of hydrogen bond formation with water and the intermolecular hydropholic force. The isomerization of a small number of azobenzene chromophores (2-3 mol %) effects the balance, resulting in an efficient phase separation. 

The steeper slope of the T c, , ., -M dependence versus that of the Tk-i(lc) dePendence has ev K ore important implications on the moledular weight-phase transition temperature dependence for the situation when the monomer structural unit displays only a monotropic or a virtual mesophase (Figure 10). 

Titania. Titania powders are used as pigments, catalytic supports, membranes, opacifiers, photocatalysts and fillers in industrial applications . Titania particles have been prepared by a number of methods, such as hydrolysis, sol-gel, microemulsion and hydrothermal synthesis. Titania exists naturally in two tetragonal forms, the metastable phase anatase, and the stable phase rutile. On heat treatment, anatase transforms into rutile. The phase transition temperature depends on the starting materials and the preparation procedure. 

As already mentioned, the phase transition temperature depends on the phospholipid structure, i.e. the number and conformation of double bonds, length of fatty acid chains, charge and volume of phospholipid head group, hydrogen bonds etc. The latter are important for the stabilization of the membrane and an increase in T,. 

Based on this measurement strategy, the phase transition temperature of a responsive system can be determined as a function of the liquid environment or the material parameters. This is demonstrated by Jhon et al. (2(X)6) for grafted PNiPAAm films and different salt concentrations in the medium. For an increasing NaCl concentration up to 1 M, a depression of the phase transition temperature of several K is observed. The study of Kauftnann et al. (2010) investigates copolymers of NiPAAm and carboxyal-kylacrylamide. QCM-D reveals the shift of the phase transition temperature depending on different alkyl chain length and comonomer fractions. 

Almost of all polymers belong to the 2) group behaves quite similar to those of aqueous PNiPAM solutions described above and show that the phase transition temperatures depend mainly on their own primary structure as represented in Fig 14... 

Figure 18 Molecular weight dependencies of the phase transition temperature (T,) from orthorhombic to hexagonal phase and the melting temperature Tm) of the hexagonal phase of PE. O = phase transition from orthorhombic to hexagonal phase A A = melting of the hexagonal phase. (From Ref. 131.)...

In a fundamental sense, the miscibility, adhesion, interfacial energies, and morphology developed are all thermodynamically interrelated in a complex way to the interaction forces between the polymers. Miscibility of a polymer blend containing two polymers depends on the mutual solubility of the polymeric components. The blend is termed compatible when the solubility parameter of the two components are close to each other and show a single-phase transition temperature. However, most polymer pairs tend to be immiscible due to differences in their viscoelastic properties, surface-tensions, and intermolecular interactions. According to the terminology, the polymer pairs are incompatible and show separate glass transitions. For many purposes, miscibility in polymer blends is neither required nor de-... 

The question arises as to how useful atomistic models may be in predicting the phase behaviour of real liquid crystal molecules. There is some evidence that atomistic models may be quite promising in this respect. For instance, in constant pressure simulations of CCH5 [25, 26] stable nematic and isotropic phases are seen at the right temperatures, even though the simulations of up to 700 ps are too short to observe spontaneous formation of the nematic phase from the isotropic liquid. However, at the present time one must conclude that atomistic models can only be expected to provide qualitative data about individual systems rather than quantitative predictions of phase transition temperatures. Such predictions must await simulations on larger systems, where the system size dependency has been eliminated, and where constant... 

Fr kjaer et al., 1984 Grit et al., 1989). An example of the pH dependency on the hydrolysis rate of liposomes consisting of soybean phosphatidylcholine is presented in Fig. 6. Hydrolysis kinetics changed rather abruptly around the phase transition temperature. 

Recently, due to increased interest in membrane raft domains, extensive attention has been paid to the cholesterol-dependent liquid-ordered phase in the membrane (Subczynski and Kusumi 2003). The pulse EPR spin-labeling DOT method detected two coexisting phases in the DMPC/cholesterol membranes the liquid-ordered and the liquid-disordered domains above the phase-transition temperature (Subczynski et al. 2007b). However, using the same method for DMPC/lutein (zeaxanthin) membranes, only the liquid-ordered-like phase was detected above the phase-transition temperature (Widomska, Wisniewska, and Subczynski, unpublished data). No significant differences were found in the effects of lutein and zeaxanthin on the lateral organization of lipid bilayer membranes. We can conclude that lutein and zeaxanthin—macular xanthophylls that parallel cholesterol in its function as a regulator of both membrane fluidity and hydrophobicity—cannot parallel the ability of cholesterol to induce liquid-ordered-disordered phase separation. 

A theoretical treatment of the effect caused by the competition between the sine-like angular-dependent component of the adsorption potential and dipole lateral interaction demonstrated that the values 6 are the same in the ground state and at the phase transition temperature.81 Study of the structure and dynamics for the CO monolayer adsorbed on the NaCl(lOO) surface using the molecular dynamics method has also led to the inference that angles 0j are practically equalized in a wide temperature range.82 That is why the following consideration of orientational structures and excitations in a system of adsorbed molecules will imply, for the sake of simplicity, the constant value of the inclination angle ty =0(see Fig. 2.14) which is due to the adsorption potential u pj,q>j). 

The initial hydration rate v and the equilibrium hydration amount were obtained as parameters reflecting the hydration behavior of LB films (see Figure 8). Temperature dependencies of the hydration behavior (v0and W ) of 10 layers of DMPE (Tc = 49 °C) LB films are shown in Figure 9. Large W and v0 values were observed only around the phase transition temperature (7C) of DMPE membranes. Thus, DMPE LB films were hydrated only near the Tc, but not in the solid state below the Tc and in the fluid state above the Tc. This indicates that the... 

Marsh, D. (1991). Analysis of the chainlength dependence of lipid phase transition temperatures main and pretransitions of phosphatidylcholines main and non-lamellar transitions of phosphatidylethanolamines, Biochem. Biophys. Acta-Biomembranes, 1062, 1-6. 

William Thomson (1824—1907) became Lord Kelvin in 1892. He has several famous namesakes J. Thomson proposed die law that described the dependence of phase transition temperature on size, J.J. and J.P. Thomson (father and son) are die Nobel prize awarded physicists, etc. Thus, to avoid misunderstanding we refer W. Thomson as Kelvin by analogy with J.W. Strutt (1842-1919), who got his title (Lord Rayleigh) in 1873 by the inheritance. 

Fig. 9 Temperature dependence of 5iso for the NMR peaks in squaric acid in the close vicinity of the phase transition temperature left panel). Note that the change starts as a smooth curve, followed by a jump caused by the first-order character of the phase transition. This is considered evidence for the coexistence of an order/disorder and displacive character in the phase transition mechanism [20]. The right panel gives a comparison between theoretical and experimental data. For details, see text...

Fig. 18 Temperature dependence of the CPMAS spectra of NH4H2ASO4 around the antiferroelectric phase transition temperature. The peaks corresponding to the paraelec-tric and antiferroelectric phases are labelled P and AF, respectively...

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