Gauche link

Here, tg is the energy difference between a trans and a gauche link and the number of gauche links in the spacer is g. The term g g=F g g=F is the additional energy resulting from the so-called pentane effect produced by a g g=F sequence in the spacer. Within the nematic phase the more anisotropic conformers are favored, as we have seen, and the conformational distribution becomes [66]... 

A cross-linked polymer has a density of 0.94 g cm" at 25°C and a molecular weight between crosslinks of 28,000. The conformation of one bond in the middle of the molecule changes from trans to gauche, and the molecule opens up by 120°. In w-butane, the trans to gauche transformation requires about 3.3 kJ mol". Estimate a value for AH of stretching based on this model, and use the law of cosines to estimate the magnitude of the opening up that results. 

Furthermore, in the same study [47] it was shown that the maximum rate of increase in the LMP occurs between 180 and 200 °C and that the percentage of the macromolecule trans-conformations increased in proportion to the heat of fusion or annealing. The trans-conformation has a torsion angle equal to 160° around the 0-CH2-CH2-0 link compared to 60° for the gauche-conformation [80],... 

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