Structural Regulation of Poly(benzoxazole imide)s and Their Composites with Fluorinated Graphene to Construct High-Performance Low Dielectric Films

The poor processability has long limited the broad application of polybenzoxazoles in microelectronics. Herein, a series of poly(benzoxazole imide) (PBOI) copolymers were designed and prepared through the polymerization of 5-amino-2-(4-aminobenzene) benzoxazole with 3,3′,4,4′-biphenyl tetracarboxylic dianhydride and 4,4′-(hexafluoro-isopropylidene)diphthalic anhydride. These PBOI copolymers show excellent film-forming properties by integrating preformed benzoxazole structures into the polyimide backbone. Moreover, the molecular and aggregate structures of PBOIs, such as chain rigidity and stacking behavior, can be facilely regulated by controlling the comonomer ratio, thereby significantly affecting their macroscopic properties. A breakthrough in film performance could be further achieved by compounding PBOIs with fluorinated graphene (FG) via in situ polymerization. This series of FG/PBOI composite films exhibit high mechanical strength (119.8–371.2 MPa), modulus (2.5–6.7 GPa), heat resistance (5% weight loss, 551.3–620.6 °C), and hydrophobicity (water absorption within 72 h, 0.8–2.5%) as well as a low dielectric constant (2.09–3.4), which can well meet the development needs of microelectronic packaging. This work is also believed to provide theoretical guidance for the structural design and performance research of high-performance dielectrics.