Poly(benzoxazole-amide-imide) copolymers for interlevel dielectrics: interchain hydrogen bonding, molecular arrangement and properties

A series of novel random poly(benzoxazole-amideimide) copolymers were synthesized via the poly(amic acid)s from the reaction of 5-amino-2-(4-aminophenyl)benzoxazole (BOA) and 4-amino-N-(4-aminophenyl)benzamide (DABA) with 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA). The corresponding homopolyimides were also prepared for comparison. The chemical composition, interchain hydrogen bonding and molecular arrangement of the copolyimides in solid films were investigated by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, computation techniques and wide angle X-ray diffraction (WAXD). The results indicated that the interchain hydrogen bonds were most likely formed between the amide oxygen atoms and -N-H bands. And the ordered chain packing structures of copolyimide films were completely different from those of the homopolyimide films probably due to the directional interchain hydrogen bonding interactions. The properties of the copolyimides were also well-characterized by tensile tests, dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA) along with water absorption, solubility and peel tests. All of the obtained copolyimide films exhibited high tensile strength (321 similar to 332 MPa) and modulus (6.76 similar to 8.03 GPa) without any stretching. Moreover, the glass transition temperatures (T(g)s) and 5 % weight-loss temperatures of the copolyimides in nitrogen were above 322 and 560 degrees C, respectively. Additionally, the copolyimide films also exhibited low water absorption, excellent chemical resistance and good adhesion properties suitable for interlevel dielectrics in microelectronics.