Glassy mesophase

Note The recommended subscript to designate a glassy mesophase is g. 

Lead(II) alkanediwoates (92), liquid-erystalline preeursors to poly(diacetylenes), have also been investigated, and are found to form highly ordered smectic structures with thermo-dynamie data similar to those of saturated lead(II) alkanoates ((91) M = Pb). In addition, they appear to form glassy mesophases at low temperatures, and thus the smectic structures can be observed at room temperature. 

In contrast to the isotropic mesophase transition, complete supercooling to the glassy mesophase state is possible. The crystallization from the mesophase may be irreversible. 

Synthetic Resins. Various polymers and resins are utilized to produce some specialty carbon products such as glassy carbon or carbon foam and as treatments for carbon products. Typical resins include phenoHcs, furan-based polymers, and polyurethanes. These materials give good yields of carbon on pyrolysis and generally carbonize directly from the thermoset polymer state. Because they form Httle or no mesophase, the ultimate carbon end product is nongraphitizing. 

Kuznetsov et al. s methodological approach [72-75] provides another example of attempts to evalue the interphase thickness experimentally. Their approach was based on the hypothesis that the mesophase remains glassy while the bulk of the binder has already passed to the highly elastic state. Investigating the concentration... 

Figure 5 presents the results of tensile tests for the HPC/OSL blends prepared by solvent-casting and extrusion. All of the fabrication methods result in a tremendous increase in modulus up to a lignin content of ca. 15 wt.%. This can be attributed to the Tg elevation of the amorphous HPC/OSL phase leading to increasingly glassy response. Of particular interest is the tensile strength of these materials. As is shown, there is essentially no improvement in this parameter for the solvent cast blends, but a tremendous increase is observed for the injection molded blend. Qualitatively, this behavior is best modeled by the presence of oriented chains, or mesophase superstructure, dispersed in an amorphous matrix comprised of the compatible HPC/OSL component. The presence of this fibrous structure in the injection molded samples is confirmed by SEM analysis of the freeze-fracture surface (Figure 6). This structure is not present in the solvent cast blends, although evidence of globular domains remain in both of these blends appearing somewhat more coalesced in the pyridine cast material.

These recent theoretical results are of evident interest as they permit to a certain extent, to construct macromolecules of LC polymers with predetermined molecular parameters x1( x2 and x3. The above model probably lacks perfection because already cases are known when a spacer group partially takes part in mesophase formation (in contrast to the postulate of the work cited). It is, besides, well known that LC polymers are characterized with anomalously high relaxation times and a tendency towards the frozen glassy state. This implies that kinetic considerations should necessarily be involved to analyze the possibilities of formation of various meso-phases. This approach should be further expanded to polymers with mesogenic... 

Cr Cub, Cubv d E G HT Iso Isore l LamN LaniSm/col Lamsm/dis LC LT M N/N Rp Rh Rsi SmA Crystalline solid Spheroidic (micellar) cubic phase Bicontinuous cubic phase Layer periodicity Crystalline E phase Glassy state High temperature phase Isotropic liquid Re-entrant isotropic phase Molecular length Laminated nematic phase Correlated laminated smectic phase Non-correlated laminated smectic phase Liquid crystal/Liquid crystalline Low temperature phase Unknown mesophase Nematic phase/Chiral nematic Phase Perfluoroalkyl chain Alkyl chain Carbosilane chain Smectic A phase (nontilted smectic phase)... 

Drozd-Rzoska, A., Rzoska, S. J., and Czupiyhski, K. (2000) Phase transitions from the isotropic liquid to liquid ciystalhne mesophases studied by linear and nonlinear static dielectric permittivity, Phys. Rev. E 61, 5355-5360 Rzoska, S. J., Paluch, M., Drozd-Rzoska, A., Paluch, M., Janik, P., Ziolo J., and Czupryhski, K. (2001) Glassy and fluidlike behavior of the isotropic phase of mesogens in broad-band dielectric, Europ. Phys. J. E 7, 387... 

Xii and x can be measured directly by orientation of an aligned liquid crystal with the director parallel or perpendicular to the magnetic field. This implies that the measurements are carried out in a magnetic field that is not strong enough to reorient the liquid crystal. Alternatively, the aligned mesophase can be frozen into the glassy state. The xii and x ... 

Serrano and co-workers have reported the synthesis of two interesting series of chiral, hexacatenar metal complexes, that is, mono- and dinuclear, derived from chiral oxazoline-based ligands.None of the pure dinuclear compounds (136 X = OAc, Cl) was mesomorphic and most were room-temperature oils or glassy materials. This is likely due to the sterically demanding central chiral unit preventing molecular stacking and, hence, mesophase formation. 

The typical LCP character, resulting from the combination of LC and polymeric features, is primarily reflected in the phase behaviour. In analogy to LMLCs, LCPs exhibit various mesophases (see Fig. 2), often broadened in comparison to those of the monomeric systems. Likewise, the polymeric nature also dominates the behaviour in the solid phase below the anisotropic melt. Here, semicrystalline or glassy states are reported, which are very common for conventional non-mesomorphic polymers. 

So far, the discussion has been restricted to isolated motions of single molecules. In LCPs, however, collective motions of a lar number of molecules may occur. For the latter mechanism, known as order director fluctuations, a broad distribution of correlation times is sedicted [%, 37]. In contrast to the isolated modes, discusred above, director order fluctuations are expected to occur only in the mesophase of LCPs, but should be completely absent in the solid and glassy state of these systems. 

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