Polyimide synthesis, rapid

A new facile method for the rapid synthesis of aliphatic polyamides and polyimides was developed by using a domestic microwave oven to facilitate the polycondensation of both w-amino acids and nylon salts as well as of the salt monomers composed of aliphatic diamines and pyromellitic acid or its diethyl ester in the presence of a small amount of a polar organic medium. Suitable organic media for the polyamide synthesis were tetramethylene sulfone, amide-type solvents such as A -cyclohexyl-2-pyrrolidone (CHP) and 13-dimethyl-2-imidazolidone (DMI), and phenolic solvents like m-cresol and c)-chlorophenol, and for the polyimide synthesis amide-type solvents such as A-methyl-2-pyrrolidone, CHP, and DMI. In the case of the polyamide synthesis, the polycondensation was almost complete within 5 min, producing a series of polyamides with inherent viscosities around 0.5 dL/g, whereas the polyimides having the viscosity values above 0.5 dL/g were obtained quite rapidly by the microwave-assisted polycondensation for only 2 min. 

Polyimide Synthesis from Nylon-Salt-Type Monomers. The microwave-assisted polycondensation was further applicable to the effective, rapid synthesis of aliphatic polypyromellitimides from the salt monomers XPMA and XPME composed of aliphatic diamines and both pyromellitic acid PMA and its diethyl ester PME (Eqs 3 and 4). 

Jmai", Y.i Rapid Synthesis of Polyimides from Nylon-Salt Monomers. Vol. 140, pp. 1-23. 

Rapid Synthesis of Polyimides from Nylon-Salt-Type Monomers... 

Thus, we have recovered the lost salt monomer method for a facile and versatile synthetic method for polyimides. This chapter reviews our recent findings on the rapid synthesis of a series of polyimides by the salt monomer method. This also includes the properties of newly synthesized aliphatic polyimides, and the application of the salt monomer method as well. 

In a brief summary, we have developed a facile and versatile asalt monomer method for the rapid synthesis of both aliphatic and aromatic polyimides. The salt monomer method has the following advantages over the conventional two-step method. First, the aliphatic-aromatic salt monomers as well as all aromatic, composed of diamines (both aliphatic and aromatic) and aromatic tetracarbox-ylic acids (or their half diesters) are highly reactive and rapidly produce polyimides with high molecular weights in one step by the solid-state thermal poly-... 

Here we have combined the salt monomer method with microwave-induced polycondensation for the synthesis of aliphatic polyimides P-XPM from salt monomers XPMA and XPME (see Eq. 5, X=6-12, Ar=PM, and R=H and ethyl) [28]. When DMI or CHP was used as the solvent, the polycondensation of both salt monomers proceeded quite rapidly, and only 2 min of microwave irradiation readily afforded the aliphatic polyimides with inherent viscosities around 0.7 dL/g or above. Under these microwave irradiation conditions, salt monomers XPME were found to be more reactive than salts XPMA, judging from the attained inherent viscosity values. 

In short, the microwave energy was successfully applied for the first time for the rapid synthesis of condensation polymers such as polyimides and polyamides from the salt monomers (and co-amino acids) by using a simple domestic microwave oven. The rapid polymer formation is caused by the efficient internal heating of the reactants. This compares favorably with the long reaction time required for the conventional thermal polycondensation with external heating. 

Imai Y (1996) A new facile and rapid synthesis of polyamides and polyimides by microwave-assisted polycondensation. In Hedrick JL, Labadie JW (eds) Step-growth polymers for high-performance materials. Am Chem Soc Washington, p421... 

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