Intrinsic ultralow Dk/Df polyimides with hydrophobicity and high adhesion based on a molecular threading and interlocking mechanism

Concurrently improving the dielectric properties, water resistance, and adhesion of polyimides is crucial for their practical use in microelectronics. Herein, series polyimides (PISTs) were designed and prepared through multicomponent copolymerization by incorporating both triptycene and linear siloxane units into a fluorinated polyimide system. The incorporation of triptycene diamine (DAT) with a rigid caltrop-like configuration restrained the thermal motion of siloxane segments (APTMDS) and prevented the close stacking of molecular chains through the mechanical interlocking effect while maintaining its high adhesion and hydrophobicity, which was confirmed by DMA, WAXD measurements, and molecular dynamics simulation (MD) method. The as-prepared polyimide (PIST-0.25) with an optimal triptycene content achieved a markedly low dielectric constant (Dk = 2.18) and dielectric loss (Df = 0.00136), combined with low water absorption (0.16 %), high peel strength to copper foil (1.06 N/mm), and good solubility. This combination of properties demonstrates significant potential for microelectronic substrates.