Hyperbranched-polysiloxane-based hyperbranched polyimide films with low dielectric permittivity and high mechanical and thermal properties

A series of hyperbranched polysiloxane (HBPSi)-based hyperbranched polyimide (HBPI) films with low dielectric permittivity and multiple branched structures are fabricated by copolymerizing 2,4,6-triaminopyrimidine (TAP) with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 4,4′-diaminodiphenyl ether, and HBPSi via the two-step polymerization method. The dielectric permittivity of HBPSi hyperbranched polyimide films decreases with increasing TAP fraction, namely, from 3.28 for sample PI-1 to 2.80 for PI-4, mainly owing to the enlarged free volume created by the incorporation of multiple branched structures. Moreover, HBPSi HBPI possesses desirable solubility and good mechanical properties and thermal stability. PI-4 not only has low dielectric permittivity (2.80, 1 MHz), excellent solubility (soluble in several common organic solvents), and remarkable thermal properties (glass-transition temperature of 273 °C, 5% weight loss temperature of 498 °C in N ₂ and 486 °C in O ₂ ), but it also demonstrates admirable mechanical properties with a tensile strength of 103 MPa, elongation at break of 7.3%, and a tensile modulus of 2.16 GPa. HBPSi HBPI might have potential applications in interlayer dielectrics and other microelectronics fields.