Synthesis of ladder polybenzoisoquinoline

It is known that rigid-chain cyclic polymers, such as polyimides, polybenzimidazoles, pyrroes considerably surpass polymeric materials on thermostability on the basis of known thermosetting resins. The reaction of cyclopolycondensation of 2,3,7,8-tetraaminodibenzop-dioxin and 1,4,5,8-naphthalenetetracarboxylic acid dianhydride in a solution of polyphosphoric acid gave a high molecular weight (ηpr 4.76 dl/g) ladder polybenzoisoquinoline. The structure of the obtained polymer is confirmed by elemental analysis, IR and EPR spectroscopy. The solubility and thermal stability of polybenzoisoquinoline were determined. The polymer is highly resistant to various reagents, both acidic and basic characters.