Synthesis and Properties of Heat-resistant Polyimides Films Containing Crosslinkable Group-tetrafluorostyrene

Polyimide (PI) is widely used in high-tech fields such as microelectronics, aerospace, and national defense because of its excellent optical properties, high- and low-temperature resistance, and good dimensional stability. To achieve the desired properties of PI, the monomers 2,6-diaminopyrimidin-4-ol (DAPD) and 6-(2,3,5,6-tetrafluoro-4-vinylphenoxy) pyrimidin-2,4-diamine (DAFPD), which contains crosslinkable functional groups, were designed and synthesized successfully and copolymerized with 4,4′-oxydianiline (ODA) and 4,4-hexafluoroisopropylphthalic anhydride (6FDA). The prepared PI film (PI-3), with rigid backbones and loose packing had excellent heat resistance (T_d5%=489 °C) and optical properties (T₄₅₀=82%). Furthermore, a crosslinked PI film (c-PI-3) with more heat-resistant (T_d5%=524 °C) and better mechanical properties (σ=125.46 MPa), can be obtained through thermal crosslinking of tetrafluorostyrene. In addition, the changes in the properties caused by the proportion of DAFPD added during copolymerization are discussed comprehensively. This study provides a promising candidate for heat-resistant PI materials.