Decamethylene spacer

Table 2. Triad and Dyad Polymers with a Decamethylene Spacer...

Another type of unsaturated mesogenic structure, which is based on a structure in between an azo- and vinylene-type, is that in which a Schiff base unit links two phenylene groups. This unit is similar in geometry to the three previous mesogenic units, the azo, azoxy and stilbene groups The only reported example of this structure, however, was Polymer 8 with a decamethylene spacer, and it was quite similar in properties to the polymers just discussed. It also possessed a smectic phase, and the mesogenic unit had terminal carboxy groups. 

Several different structural factors influence the properties of the mesophase in these polymers, including dipolar effects, the planarity and rigidity of the mesogenic unit, and its length-to-width ratio among others. These factors are difficult to quantify, either absolutely or relatively, but some idea of their influences can be obtained by comparing the properties of polymers with different mesogenic units when combined with the same flexible spacer. This comparison has already been made for the dyad and triad esters in Table 2, and in this section it will be extended to other types of liquid crystalline polymers which contain a common decamethylene spacer. 

A liquid crystal polyester having azoxybenzene mesogenic units and decamethylene spacers was subjected to a proton NMR study after the polymer was aligned in a magnetic field of 1 Tesla Below the melting point of the polymer, the NMR spectrum... 

Rg. 12.18 Some examples of main-chain liquid-crystal polymers (a) poly(p-phenylene benzobisoxazole) (PBO), lyotropic (b) poly(4-carboxybenzene-propionic acid), thermotropic and (c) a thermotropic polymer with a long flexible decamethylene spacer. 

In addition, the hairpin activation energy Uh can be calculated from the Arrhenius fit to the data in Figure 1.10, from which we obtain a value Uh = 3.6 kJ/mol. Noting that hairpin formation in the decamethylene spacer requires two trans-to-gauche transformations, each of which involves an energy expenditure of about 1 kJ/mol [Morrison and Boyd, 1983], it appears that the experimental result is of the correct order of magnitude. 

Adhesives based on acidic monomers with long spacers between the strongly aeidie and the polymerizable groups resulted in better performance. In ease of MDP, the good bond strengths can be explained by a self-assembled nano-layering due to the length of the decamethylene spacer and by... 

Figure 3-27. Liquid crystalline polyester with decamethylene spacers. Temperature-dependent infrared spectrum in the defect modes frequency range (see text). The spectra and shifted one from the other as in a tridimensional plot.

We prepared polymers containing the mesogenic structure 25 of Table 1, both in the homopolymer form and as copolymers containing polysiloxane and decamethylene flexible spacers, and these polymers were compared in their properties to the earlier polymers prepared with a polymethylene spacer only The polymer with mesogenic structure 32 and the siloxane spacer showed a low molar enthalpy for the melt transition, while the copolymer and the polymer with the polymethylene spacer showed quite high melt enthalpies. 

Chiral LC monomers, Ml and M2, were synthesized via the synthetic routes shown in Scheme 12.5. Ml and M2 are composed of a biphenyl moiety linked with a phenyl moiety via an ester linkage as a mesogenic core, a decamethylene or a hexamethylene chain as a spacer and an (5 )-2-fluorooctyloxy group as a terminal moiety. The other type of thiophene monomer, M3, was synthesized in a similar manner to that shown in Scheme 12.5, but the mesogenic core was a biphenyl moiety and not the three-ring moiety adopted in Ml and M2. 

In a series of liquid crystalline polyesters containing a decamethylene flexible spacer between the mesogenic units in the pol3noier backbone, Lenz and coworkers observed that a methyl, chloro, or bromo substituent on a hydroqulnone moiety (II, n=10, R=CH3,... 

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