Phenylethynyl Containing Imide Oligomers

As part of a program to develop high performance/high temperature adhesives and composite matrices for a Mach 2.4 high speed civil transport, imide oligomers containing phenylethynyl groups were investigated. Phenylethynyl groups were placed on the ends of oligomers of different molecular weights (1250, 2500 and 5000 g/mol), pendent along the backbone of oligomers and both pendent and terminal on oligomers. Many different compositions of phenylethynyl containing imide oligomers had been previously prepared and evaluated before selecting the composition based upon 3,3'.4,4'-biphenyltetracarboxcylic dianhydride (BPDA), 3.4'-oxydianiline (3,4'-ODA) and 1,3-bis(3-aminophenoxy)benzene (APB) for extensive work. 4-Phenylethynylphthalic anhydride (PEPA) was used to place phenylethynyl groups on the ends of the oligomers and 3,5-diamino-4'-phenylethynylbenzophenone (DPEB) was used to introduce pendent phenylethynyl groups along the oligomeric backbone. Upon heating above 300 C, the phenylethynyl groups react to provide chain extension, branching and cross linking. Several of these materials exhibited excellent properties as adhesives and composite matrices. The chemistry, processability and properties of the oligomers, the cured polymers, bonded specimens and composites from phenylethynyl containing oligomers are presented.