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A method was developed for synthesis ofpoly-p-phenylenebenzobisthiazole (PPBT)from 2, The thermostable polymer fibres with a high modulus of elasticity and low density used in composite materials for aerospace engineering are of great practical interest. Fibres based on aromatic heterocyclic polymers occupy a special position among them. The rod-shaped macromolecules of polyheterocycles have high equilibrium rigidity quantitatively estimated by the value of the Kulm segment. The Kuhn segment of poly[(benzo[l,2-d:4,5d']bisthiazole-2,6-diyl)-l,4-phenylene] (PPBT) is 106 nm, which is greater than the value of the Kuhn segment for other rigid-chain polymers [1]. The greater skeletal rigidity of macromolecules of PPBT and the ability of its solutions to pass into the liquid-crystalline state in a certain concentration are responsible for the high mechanical properties of the fibre. Fibres spun from a liquid-crystalline solution of PPBT have a unique modulus of elasticity (300-350 GPa) close to the modulus of elasticity of several types of carbon fibres together with excellent thermal stability and strength (3000-3600 MPa) [2,3].PPBT is synthesized [4-6] in a one-stage reaction of cyclopolycondensation of terephthalic acid (TPA) with 2,5-diamino-1,4-dimercaptobenzene (DADMB) in a solution of polyphosphoric acid (PPA). Due to the instability of DADMB, it is used in the form of DADMB dihydrochloride [4][5][6]. The reaction takes place according to the scheme All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi.

Bei katalytischen Hydrierungen der Dinitrobenzanilide (I) und (IV) entstehen primär die Aminonitroverbindungen (II) und (V).

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