Role De La Masse Moleculaire Dans L'apparition Des Phases Nematiques Thermotropes

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Abstract
The thermotropic nematic phases of pure aromatic oligo and polyazomethines and their binary mixtures in a nematic solvent of the same chemical nature have been studied by optical microscopy. The transition temperatures of the pure compounds increase very rapidly with molecular weight; the polymeric materials decompose before melting. When a methyle group is randomly fixed on the phenylene diamine rings, the melting temperature of the crystal is depressed; this is a good way of helping the formation of thermotropic nematic phases with rigid polymers. Apart from the solution of the 3 ring compound in the nematic solvent, the mixtures we have considered are not ideal.