Octamethylene diamines

The first patent of Edwards and Robinson147 claims the condensations of pyromel-litic acid and aliphatic diamine salt to prepare polyimide. Recently, that approach has been revisited, and biphenyl tetracarboxylic and pyromellitic acids give a salt monomer by reaction with 1 mol of an aliphatic diamine (octamethylene diamine and dodecamethylene diamine). The salts were polymerized under 250 MPa at 250°C for 5 h in closed reaction vessels (Fig. 5.32) giving crystalline polymers.148 By reaction of pyromellitic tetraacid with oxydianiline, it has been possible to isolate a monomeric salt. It was polymerized under 30 MPa giving a PMDA-ODA polyimide with water elimination. 

Typical comonomers — Aliphatic amines Heptamethylene diamine, — octamethylene diamine, decamethylene diamine, cyclohexyl diamine... 

If the methylene chain is increased by one unit (2), the 4 1 complex does not appear to be stable. Only the 2 1 complex is shown in the titration behavior. However, the exact structure of the complexes are unknown. The octamethylene compound forms only 2 1 complexes and, presumably, so do the other diamines with more than three carbons in the chain. 

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