Investigation of Nitrogen-Rich Polymers based on tetrazoles and triazoles (2010)

The aim of this thesis was the development of new nitrogen-rich, energetic polymers based on tetrazoles and triazoles, along with the development of energetic materials related with the polymers. The demand to the polymers was the suitability as energetic binders. Therefore, the polymers should possess high thermal and physical stabilities, in order to stabilize the energetic filler, along with moderate to good explosive characteristics. Moreover, a high stability towards chemical reactions is mandatory to prevent reactions between the polymer and the energetic filler. The thesis can be divided into six parts. The first chapter deals with energetic materials based on tetrazolyl hydrazines. Besides nitrogen-rich polymers, obtained either by radical polymerization (poly(methyl-1-(1-vinyl-1H-tetrazol-5-yl)hydrazine)) or polycondensation reactions, 5-azido-1H-tetrazoles and functionalized tetrazenes were synthesized. The nitrogen-rich polymers prepared by polycondensation reactions of the 1,1-methyl-1Htetrazolylhydrazine possess a high thermal stability (>240 °C) and are insensitive towards impact and friction. The advantage of these polymers is that the functional groups are stabilized by the formed carbamates, reducing the chemical reactivity. Nevertheless, the NH-proton of the carbamate structure is able to form hydrogen bridges, leading to increased adhesion forces between the energetic filler and the polymer. The energetic polymers formed by radical polymerization bear hydrazine moieties that increase the solubility in acids, along with possible adhesion forces with energetic fillers. The 5-azido-1H-tetrazoles were prepared by diazotation of tetrazolyl hydrazines. The performance of the ethyl bridged 5-azido-1H-tetrazoles reached the values of RDX but the compound proved to be much too sensitive towards impact and friction to find any application. The tetrazenes instead possess suitable thermal and physical stabilities along with good to moderate energetic properties. They were prepared by oxidation of tetrazolyl hydrazines, leading to the corresponding “dimer. The second and third part of the thesis deals with complexes, either of the 5-carboxylic-1Htetrazolate (part two) or bidented and tridented tetrazole ligands. The aim of the preparation of complexes was the synthesis of new coloring agents for pyrotechnical formulations. Therefore, the barium, strontium and copper 5-carboxylic-1H-tetrazolate were investigated. The complexes showed a high thermal and physical stability. In contrast to the 5-carboxylic-1H-tetrazolates, the i copper complexes of (2-(1H-tetrazol-1-yl)ethyl)amine and 1,2-bis(5-monomethylhydrazinyl-1Htetrazolyl)ethane were very sensitive towards impact and friction. Moreover, the decomposition points of the complexes were lower than the decomposition points of the ligands themselves. An explanation could be the close arrangement of the ligand and the oxidising nitrate anion next to each other. Besides tetrazoles, polymers based on triazoles were synthesized. The triazoles containing polymers were prepared by the reaction of acetylene derivatives with azide containing polymers (polyvinylazide and glycidyl azide polymer). The energetic polymers obtained can be divided in three classes: polymers containing nitrate esters, azide groups and nitramines. The nitrate esters were sensitive towards impact and possess a low thermal stability. The azide polymers were more sensitive towards physical stimuli than the nitrate esters, but possessed higher decomposition points. The nitramine containing polymer possessed the highest thermal stability, but proved to have only low energetic properties. Another chapter of this thesis deals with the investigation of thiatriazoles. This strictly academic topic resulted of fruitless trials of another synthetic pathway for tetrazolyl hydrazines. Nevertheless, the several thiatriazoles were synthesized and investigated. The last topic of this thesis are alkylated N,N-dinitramines. These compounds are known for a long time, but were not characterized properly. Therefore, we investigated two different synthetic pathways and determined the physical and thermal stabilities along with the explosive properties. The first preparation was published by Russian chemists and deals with alkylation reactions of silver dinitramide salts. Despite our efforts, we were not able to isolate any alkyl N,N-dinitramine using this route. The N,N-dinitramines were prepared according to patents by the nitration of alkyl nitramines using nitronium tetrafluoroborate. The nitramines proved to be moderate explosives, whereas the corresponding N,N-dinitramines can be classified as high explosives. The low decomposition points of the N,N-dinitramine at about 80 °C prevents these compounds from being used as explosives.