Orientational ordering compressed monolayers

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). 

Orientational ordering transitions [394] clearly occur in the commensurate phase (possibly in coexistence with the fluid) up to 1.101 monolayers at 28.1 K, as well as in the uniaxial compressed phase from 1.142 to 1.178 monolayers at 29-30 K based on adiabatic calorimetry [156] a heat capacity peak at 28.7 K was reported at a coverage of 1.109 which was interpreted as the transition to the uniaxially compressed incommensurate phase, whereas this peak is located near 27.5 K in the submonolayer regime. The ac heat capacity scans [394] in the triangular incommensurate phase at 1.200 and 1.302 monolayers show only very weak and broad features in the relevant temperature range from 22 K to 32 K. Thus, it is concluded [394] that their orientational order is only gradually lost as the temperature is increased... 

F re 36. Compressed-monolayer and low-temperature phase diagram of N2 on graphite (solid lines) based on heat capacity measurements. Filled circles represent positions of heat capacity peaks. Hatched regions denote two-phase coexistence, and dashed lines as well as boundaries separating UIO -I- TI, UID, and TI phases are speculative. The following abbreviations have been used Commensurate -73 solid (C), incommensurate Vs solid (I), uniaxial (U), triangular (T), orientationally disordered (D), orientationally ordered (O). (Adapted from Fig. 2 of Ref. 394.)... 

The ( /3 X y/3)R30° in-plane (2 x 1) herringbone monolayer was found to be the most stable configuration for all types of modeling [298]. The uniform uniaxial incommensurate monolayer has also in-plane herringbone orientational order even up to higher compressions, and a search for a stable out-of-plane herringbone monolayer of the type shown in Fig. 4c led to no viable candidates. However, pinwheel stmcmres exist for certain potential... 

Figure 46. Phase diagram of N2 on graphite based on adiabatic heat capacity data coverage is reported in units of the complete n/S monolayer. Orientationally ordered commensurate phase (CO), orientationally disordered commensurate phase (CD), orientationally ordered uniaxially compressed incommensurate phase (UIO), orientationally disordered uni-axially compressed incommensurate phase (UID), triangular compressed incommensurate phase (TI), fluid phase (F), speculative reentrant fluid phase (RF). The measurement path for the highest coverage in Fig. 45 is sketched by the dashed line. (Adapted from Fig. 10 of Ref. 156.)...

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