High-Pressure Synthesis of Aliphatic Polyimides

A variety of methods are known for the synthesis of polyimides and other condensation polymers, however, the application of high pressure has seldom appeared in the literature to date. Early in 1969 Morgan and Scott reported on the high-pressure polycondensation and simultaneous hot-pressing of intractable polybenzimidazopyrrolone, that is infusible and insoluble, directly from the combination of 3,3f,4,4f-tetraaminobiphenyl and pyromellitic dianhydride (Eq.6) [29,30]. 

Ikawa et al. studied the the high-pressure synthesis of aliphatic polyamides such as 11-nylon and 12-nylon starting from the corresponding co-amino acids (Eq.7) [31,32]. 

Quite recently, we have investigated systematically the high-pressure polycondensation leading to the formation of a variety of polyimides, and polyben-zoxazoles as well [19,33]. Here we applied the salt monomer method to the high-pressure synthesis of aliphatic polyimides. 

In practice, the high-pressure polycondensation of the salt monomers producing polyimides was carried out by using a piston-cylinder type hot-pressing apparatus with the use of a Teflon capsule as a reaction vessel (see Eq. 5) [34]. 

The results of the high-pressure polycondensations of the aliphatic-aromatic salt monomers XPMA, XBPA, XTPE, XOPA, and XBTA under 200-600 MPa at 220-320°C for 3-30 h leading to the formation of a series of aliphatic polyimides (see Eq. 5) are summarized in Table 1 [22,24-26]. 

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