New polymer syntheses II--linear unsaturated polyesters containing azo groups*

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Abstract
Linear unsaturated polyesters, characterized by the presence along the polymer chain of azo groups between aromatic rings, have been prepared by reacting 3,5-bis(p-hydroxybenzylidene)isopropyl piperidinone (BHIP, I) or 3,5-divanillylidene isopropylpiperidinone (DVIP, It) with 4,4'-azodibenzoyl chloride (III) and 3,3'-azodibenzoyl chloride (IV) using the interfacial polycondensation method. The polymers were characterized by elemental analyses. IR spectroscopy, solubility and viscomnetry. The thermal properties of the polymers were evaluated by thermogravimetric analysis (TGA) and correlated to their structural units. Al] the polymers dissolved readily in concentrated H2S04 or o-cresol. X-ray analysis of the polymers showed some degree of crystallinity in polymers VI and VII. Moreover, the UV-visible spectra of certain polymers were measured in NMP or in dimethyl suiphoxide (DMSO)solutions and showed characteristic absorption bands at 412 and 432 nrn due to n-7r* transition.