LOW DIELECTRIC-CONSTANTS OF SOLUBLE POLYIMIDES BASED ON ADAMANTANE

This work synthesizes new adamantane-based polyimides by reacting 1,3- bis[4-(4-amino-phenoxy)phenyl]adamantane (4) with various aromatic tet racarboxylic dianhydrides. The poly(amic acid)s have number-average mo lecular weights (M-n) of 39 000-139 000. The M-n's of soluble polyimid es 7(d) and 7(e) are 108 000 and 89 000, respectively. These films hav e low dielectric constants ranging from 2.77 to 2.91 and low moisture absorptions of less than 0.46%. Two of these polyimides have good solu bilities, and even nonfluorinated polyimide 7(e) can be soluble in chl oroform. All polyimides 7 formed tough and transparent films. These fi lms have tensile strengths of 88.2-113.5 MPa, elongations to break of 5.6-12.5%, and initial moduli of 2.0-2.2 GPa. Dynamic mechanical analy sis (DMA) reveals that adamantane-based polyimides have two relaxation s on the temperature scale between 0 and 350 degrees C. The subglass r elaxations of polyimides 7 do not occur at the same temperature; inste ad, they range from 100 to 175 degrees C. Differential scanning calori metry (DSC) and DMA reveal their glass transition temperatures (T-g's) were found to be 232-330 and 262-343 degrees C, respectively These T- g's lie in a manageable temperature range for processing in melt.