Cross-coupling 285 preferred conformation

Networks realized in a mesophase exhibit specific behavior It was found that cross-linking in a liquid-crystalline phase results in an increase in the stability of this phase [92, 103, 133], which is in agreement with the theoretical predictions (Sec. 3.1.2). This stabilization was noted as considerably greater in the case of a smectic phase than for a nematic one [ 103]. Coupling between mesogenic order and the main chain results in a preferred conformation arrangement of... 

The most characteristic coupling constant in indazoles is the cross-ring Vs, present both in indazoles and in isoindazoles unsubstituted in positions 3 and 7. 2-Methyl isomers show an additional Vmc.h coupling which can serve to identify an isoindazole unsubstituted in position 3. In 3-azidoindazole, as in 3-azidopyrazole (56), the prototropic exchange is slowed down sufficiently to allow the measurement of a zig-zag /i,4 coupling constant. The deshielding effects observed in A-acetyl derivatives, e.g. 1-acetyl (60) on H-7 and 2-acetyl (61) on H-3, are related to a preferred E conformation (Section 4.04.1.4.3). 

The elastomer that has preferable intralayer cross-linking (El, see Fig. 7) shows completely different behavior (see Fig. 12) (18,38). In this case, the switching time increases by less than a factor of 2, the polarization can still be determined, and measurement of the ferroelectric hysteresis shows no stabilization of the switching state present during cross-linking. Then, the coupling between the orientation of the mesogens and the network conformation is obviously very... 

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