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 N2 and 486 °C in O2), 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.