Other hydrazine-containing polyurethane thermoplastic elastomers

Other hydrazine-containing polyurethane thermoplastic elastomers 

The asymmetric dimethylhydrazine (ADMH) has been used in the chemistry of macromolecular compounds mostly as polymer modifier [18]. The peculiarities of the reactivity of the tertiary nitrogen atom in ADMH result in the formation of hydrazinium compounds. Only at steric hindrance by quaterniza-tion, the nitrogen atom of the amine group can become reactive. 

At a non-stoichiometric ratio of the reagents, one can prepare a crosslinked polymer by two-step synthesis. A different result is obtained in the reaction of the polyurethane prepolymer (PP, dissolved in DMF) with ADMH [19,20]. At a 2-, 5-, and even 10-fold increase of the PP molar fraction, DMF-soluble macromolecular compounds are formed. The respective solution-cast films have mechanical properties similar to those of classical polyurethane elastomers (Table 3). 

The intrinsic viscosity, [ri], varies in different ways with the increase of the PP content (Table 3). Usually, the decrease of the viscosity of polymers (of the same molecular weight) is an evidence of macromolecules of the branched type, except for the case of comparable lengths of the branches and of the main chain, when the molecule has the shape of a star [1]. 

The structural analysis of the samples PP ADMH = 2 1 obtained at 60 and 80°C in the absence of catalysts shows the formation of a branched structure at temperatures lower than those required for the formation of allophanate (120-140°C) and biuret (100°C) structures [1]. The ability of the ADMH to form hydrazinium cations leads to the assumption that the elastomer synthesis with the participation of ADMH involves formation of reactive centers of ionic nature, similarly to the Ritter reaction, where the synthesis of the N-substituted amides of carboxylic acids passes through a stage of carbonium ion formation 

---

Other hydrazine-containing polyurethane thermoplastic elastomers... 

---