SYNTHESIS AND PROPERTIES OF PROCESSABLE POLYIMIDES CONTAINING DIACETYLENE GROUPS

Diacetylene-containing polyimides have been prepared by the oxidative coupling of new diethynyl diimide monomers. Condensation of various et hynyl-terminated amines with either 4,4'-(hexafluoroisopropylidene)dip hthalic anhydride (6FDA) or pyromellitic dianhydride (PMDA) provided t he monomers. Processability was enhanced by increasing the number of c onsecutive methylenes in the backbone, by incorporating aliphatic side chains, and for the 6FDA-based polyimides in general. The 6FDA-based diacetylene-containing polyimides are soluble in many common solvents including acetone. By controlling polymerization time, either oligomer s or polyimides can be produced in high yield. High-resolution H-1 NMR and IR spectroscopy were used to monitor the polymerization. With the exception of the polyimides containing aliphatic side groups, thermal analysis reveals a diacetylene reaction exotherm that occurs without evolution of volatile byproducts; upon thermal annealing, the exotherm disappears and these polyimides become insoluble in all common solven ts (i.e., cross-linked). Gas-transport properties are reported for one of the cross-linked 6FDA-based materials.