HEAT-RESISTANT OLIGO(PHTHALAZINONE IMIDE)S CONTAINING ARYL-s-TRIAZINE IN THE MAIN CHAIN

A novel series of soluble and curable phthalonitrile-terminated oligo(phthalazinone imide)s with well controlled molecular weights were prepared by varying the molar ratio of dianhydrides to diamines. FTIR, (1)H-NMR and elemental analysis were applied to confirm the structures of the oligomers whose molecular weights were determined by (1)H-NMR analysis. The crosslinking reactions of the phthalonitrile-terminated oligomers were performed under normal pressure in the presence of 4,4'-diaminodiphenylsulfone as catalyst at elevated temperatures to form the s-triazine rings-containing thermosetting oligo (phthalazinone imide) s. The oligomers possess good solubility in common aprotic solvents such as chloroform, pyridine, m-cresol and N-methyl-2-pyrrolidone due to the incorporation of crank, twisted and non-coplanar phthalazinone moiety into the polymer main chain,which disorders the close packing of the intermolecular chain. However, the cured samples are insoluble in all solvents because of the formation of the heterocyclic s-triazine networks during the crosslinking reaction of the cyano groups. The thermal properties of both the oligomers and the cured oligoimides were characterized by DSC, TGA and DTG. The oligomers have high glass transition temperatures (T(g)s) in the range of 200 similar to 249 degrees C. The cured samples show no T(g) from 100 similar to 400 degrees C for the heterocyclic s-triazine networks decrease the flexibility of polymer backbone. And they exhibit excellent thermal stability with 5% weight loss temperature up to 522 similar to 532 degrees C, 10% weight loss temperature ranging from 556 degrees C to 567 degrees C and the carbonized residue values at 800 degrees C in the range of 69% similar to 74%. For the excellent thermal stability of the cured oligoimides, they can be used as high performance polymeric materials in the aerospace and base materials for high temperature composite matrix.