Design and synthesis of low dielectric constant polyimides based on fluorinated diamines with twisted triphenylmethane units and bulky side chains

With the rapid advancement of 5G communication technology, the development of novel low-dielectric constant polyimides (PIs) as interlayer dielectric materials has become a key area of research. However, the development of fluorinated diamines with simple synthetic routes remains a challenge. In this study, a facile and efficient one-step synthetic strategy was employed to construct three novel fluorinated diamines with fully non-planar and twisted structures. The influence of fluorine content and different bulky side groups on the dielectric, thermal, and optical properties of the PIs based on these diamines was investigated. Notably, the increase in fluorine content and structural non-planarity significantly enhanced the dielectric properties and moisture resistance. Among the synthesized PIs, FPOPF-6FDA exhibited the most favorable performance, with a low dielectric constant (D_k = 2.20 @ 10⁸ Hz), low dissipation factor (D_f = 0.00755 @ 10⁸ Hz), low water absorption (W_A = 0.89 %), and high hydrophobicity (WC_A = 93.90°). Moreover, the non-planar and twisted fluorinated diamines did not compromise the thermal stability (T_d5 > 500 °C, T_g = 250.87–340.13 °C), optical transparency (T₅₀₀ > 85.90 %), or solubility in organic solvents of these PIs. This work provides valuable insights into the molecular design and cost-effective synthesis of high-performance low-dielectric PIs.