Polyimides Based on Non-condensed bis Naphthalic Anhydrides

However, their viscosity characteristics were low (iiiog = 0.15-0.30 dl/g), possibly due to the presence of electron-donating groups in the dianhydride component. The Tg of the resulting polymers varied in the range 253-317 °C. 

The six-membered anhydride rings exhibit a lower electrophilic reactivity than their five-membered analogs, therefore, Sek and co-workers [74] investigated catalytic systems, which show the highest efficiency in the polycondensation reactions involving six-membered anhydride rings. 

When studying the reaction of l,4-bis(l,8-dicarboxynaphthoyl-4)-benzene dianhydride with 4,4 -diaminodiphenyl oxide, it was established that, depending on the viscosity of the 

Sek and co-workers [74] note that the polymer with the highest viscosity (r red = 1-96 dl/g) was obtained using two catalysts benzoic acid (2 mol), which was added to dianhydride (1 mol) at the beginning of the reaction, and isoquinoline (2 mol), which was introduced into the reaction mixture several hours later. 

The polymers based on a dianhydrides with ether bonds and an unsubstituted central phenylene nucleus had somewhat higher viscosities as compared to the substituted structures. All the synthesised polymers were soluble in m-cresol, while the PNI bearing two substituents in ortho positions were also soluble in NMP, DMA, and DMSO. 

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