Order-disorder transition transfer

Intuitively we might associate the low shear limit with the order-disorder transition at literature data for the packing fraction in this limit is more widely scattered. We must remember that the approach to equilibrium in these systems can take a while to progress. So it is feasible that some systems have been measured away from the equilibrium state when the samples have been transferred and placed in the measuring geometry on an instrument. We could... 

Disordered O-H 0 intramolecular hydrogen bonds are not uncommon in crystal structures of molecules having cis-enol configurations, but without evidence for an order-disorder transition, they do not necessarily imply that proton transfer takes place in the crystalline state. 

FK5.6.I9 Schematic representation of the structural formation and order-disorder transition for photoactive LBK showing (A) the compressed monolayer on the water surface with densely packed chromophore side chains oriented into the gas phase and the polymer backbone facing the water surface, and (B) LBK transfer from the water to a solid support, resulting in well-ordered smetic-tike (bilayered) multilayer assemblies. (C) After phcnoinduced trars to cts isomerization, a largely disordered struaure is obtained and the layered structure is completely lost (reproduced from reference 72 with permission from Wifey-VCH). 

The mechanochemical systems may be classified according to the principle of reaction ) changes in ionisation state (hydrogen-ion transfer, ion exchange, chelation) 2) redox reaction 3) steric isomerisation 4) phase transition or order-disorder transition 5) polymer-polymer association or aggregation 6) electrokinetic processes [73]. 

The transition to super ionic conductivity (y-AgJ) is observed at 147 °C (Figurel.21). At 137 °C the wurtzite lattice is formed. The wurtzite lattice transfers into the y-Form at 147 °C connected with a jump in conductivity from 10 to 1.3 S cm . This lattice consists primarily of a phase centered iodide lattice with a highly disordered Ag+ sublattice with very mobile Ag ions. The transition to super ionic conductivity is a first-order phase transition. 

It is usual for other materials that the critical temperature (Tc) for liquid-solid or disordered-ordered phase transition increases under compression [1-3] however, the Tc for ice transferring from ice-Vlll to the proton-disordered ice-Vll phase drops from 280 to 150 K when the P is increased from 1 to 50 GPa [4—6]. Compression shortens the 0-0 distance but lengthens the H-O bond, yielding the low compressibility [7] of ice with respect to other usual materials. The liquid phase is more readily compressed than the solid phase. 

In order to investigate the phase transition in the monolayer state, the temperature dependence of the Jt-A isotherm was measured at pH 2. The molecular area at 20 mN rn 1, which is the pressure for the LB transfer of the polymerized monolayer, is plotted as a function of temperature (Figure 2.6). Thermal expansion obviously changes at around 45 °C, indicating that the polymerized monolayer forms a disordered phase above this temperature. The observed temperature (45 °C) can be regarded as the phase transition point from the crystalline phase to the liquid crystalline phase of the polymerized organosilane monolayer. 

In Figure 7 a comparison is made of the frequency of the CHj antisymmetric stretching vibration as a function of molecular area for DPPC monolayer films at the A/W and A/Ge interfaces. As described above, the frequency of (his vibration is related to the overall macromolecular conformation of the lipid hydrocarbon chains. For the condensed phase monolayer (-40-45 A2 molecule 1), the measured frequency of the transferred monolayer film is virtually the same as that of the in-situ monolayer at the same molecular area, indicating a highly ordered acyl chain, predominately all-trans in character. For LE films as well as films transferred in the LE-LC phase transition region, however, the measured frequency appears independent (within experimental uncertainty) of the surface pressure, or molecular area, at which the film was transferred. The hydrocarbon chains of these films are more disordered than those of the condensed phase transferred films. However, no such easy comparison can be made to the in-situ monolayers at comparable molecular areas. For the LE monolayers (> ca. 70 A2 molecule 1), the transferred monolayers are more ordered than the in-situ film. In the LE-LC phase transition region ( 55-70 A2 molecule 1), the opposite behavior occurs. 

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