POLYIMIDE POLYIMIDE MOLECULAR COMPOSITE FILMS - DIFFERENCE BETWEEN REACTIVE OLIGOIMIDE AND REACTIVE POLYIMIDE AS THE MATRIX COMPONENT/

Polyimide/polyimide molecular composite (MC) films were prepared by bl ending precursor solutions of a rigid polyimide and a reactive oligoim ide or a reactive polyimide that contains acetylene units in the backb one in a 7:3 ratio, followed by casting, drying and thermal imidizatio n at 300 degrees C. 3,3',4,4'-Biphenyltetracarboxylic dianhydride (BPD A), pyromellitic dianhydride (PMDA), p-phenylenediamine (PDA), oxydian iline (ODA) and 3,3'-diaminodiphenylacetylene (m-intA) were used as ac id dianhydride and diamine monomers for the preparation of polyimide. The rigid components were prepared from PMDA or BPDA and PDA. The matr ix components were prepared from PMDA or BPDA and ODA or m-intA. The p olyimide/polyimide MCs have exotherm on DSC due to the reaction of int ernal acetylene units, which indicates that the MC films are laminate processable. Tensile measurements revealed that the tensile modulus of the MCs utilizing reactive oligoimides is 20-30% higher than that of the MCs utilizing reactive polyimides. Viscoelastic analyses of the MC films showed that the crosslinking of the acetylene units gave polyim ides that have a very high glass transition temperature.