Effect of Conformational Parameters on Thermal Properties of Some Poly(oxadiazole-naphthylimide)s

Two series of poly(oxadiazole-imide)s based on naphthalene-containing anhydrides and aromatic diamines having preformed oxadiazole rings have been synthesized. One series contains four polymers: two of them are based on naphthalene-1,4,5,8-tetracarboxylic dianhydride and the other two are based on bis(ketonaphthalic-anhydride). The other series contain four copolymers based on mixtures of these dianhydrides with hexafluoroisopropylidene-diphthalic anhydride. Most of these polymers are easily soluble in polar amidic solvents and even in less polar and convenient solvents, allowing them to be processed in thin films and coatings. These polyimides and copolyimides show high thermal stability, with initial decomposition temperature being above 430°C and glass transition temperature in the range of 190-318°C. Conformational rigidity parameters of these polymers have been calculated by Monte Carlo method and discussed in relation with thermal properties. The values found experimentally for glass transition temperature correlate well with those calculated by using the conformational rigidity parameters. The dependence of glass transition temperature of these polymers on Kuhn segment can be described by linear equations, with a very good factor of convergence.