Dilute solution properties of thermotropic polymers: aromatic polyazomethines

The dilute solution properties of some polyazomethines have been investigated. Poly(nitrilo-2-methyl-1,4-phenylene nitrilomethylidine-1,4-phenylene methylidine) (MePNPM) was studied. The measurements of intrinsic viscosities, molecular weight and depolarization ratio were made in 96% sulphuric acid and in methane sulphonic acid for these polymers. A side by side aggregation is observed with time in the second solvent. In order to obtain a well defined law of viscosity, fractionation by gel permeation chromatography was made. A small amount of aggregated particles was observed for the samples which have been submitted to a thermal treatment. Nevertheless, a well defined law of viscosity has been obtained. From the viscosity law and the variation of the apparent molecular anisotropy, the rigidity of the molecule has been evaluated; the persistence length q which characterizes this rigidity has been found to equal $\text{150}\text{A}\text{?}\text{± 25}\text{A}\text{?}$.