Linear boron-nitrogen polymers

B-Aminoborazines are of particular interest for fundamental studies. In these compounds, boron is bonded to three nitrogen atoms with two different types of environment. B-Aminoborazines are also useful precursors for the synthesis of thermally stable polymers. Quite a few polycondensates of aminoborazines and copolymerisates with organic difunctional molecules have been described 4>. Of major interest are difunctional borazines yielding linear polycondensates. The condensation of l,3,5-tris(2,6-dimethylphenyl)-2,4-dichloroborazine (cf. Section II.2.5) with aliphatic, aromatic, and heterocyclic diamines, as well as the preparation of the same linear polyborazines by transamination of 1,3,5-tris(2,6-dimethylphenyl)2,4-bis(diethyl-amino)borazine with diamines was studied 139). 

Catalytic polymerization was performed in the presence of a designed composite catalytic system containing boron trifluoride-anisole complex and metaphosphoric acid for benzonitrile under a nitrogen atomosphere. The reaction temperature was lowered to about 200 C and the polymer obtained was linear and soluble, without any trace of cyclic trimers, a by-product described in the literature. But the molecular weight was in the range 1400-1700, with no obvious variation under different polymerization conditions. 

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