A new fluoropolymer having triazine rings as a dielectric material: synthesis and properties†
A novel fluoropolymer having triazine rings and thermo-crosslinkable benzocyclobutene units is prepared by a facile phase transfer catalyzed interfacial polycondensation reaction between a diphenol and a dichloro-s-triazine. This is the first example of thermo-crosslinkable fluoropolymer containing triazine units. The polymer shows a high molecular weight (Mn) of more than 70 000, good solubility and film-forming ability, as well as high storage stability. When treated at a high temperature (>200 °C), the polymer easily converts to a crosslinked network, showing a low dielectric constant (Dk) of 2.58 at a range of frequencies from 0.1 to 30.0 MHz. The Dk does not exhibit obvious change as the temperature is raised from room temperature to 100 °C. Moreover, the crosslinked network exhibits a dielectric strength of 157.7 kV cm−1, which is comparable with that of a widely used resin poly(2,6-dimethyl-1,4-phenylene ether). D–E loop tests indicate that the cured polymer possesses linear dielectric properties. The cured polymer also exhibits high hydrophobicity, which endows the polymer with a low water uptake of 0.11% after immersing it in water at room temperature for 72 h. Moreover, the crosslinked network exhibits high thermo-stability with a glass transition temperature of 264 °C and a 5 wt% loss temperature of 426 °C, as well as good mechanical properties with an average hardness of 0.48 GPa and an average Young's modulus of 11.92 GPa. These results suggest that this fluoropolymer having triazine units is better than those prepared from cyanate esters because the new polymer exhibits not only good dielectric properties, high thermostability and low water uptake, but also possesses high storage stability and good processability. Hence, this new fluoropolymer is suitable as a new dielectric matrix resin for the production of printed circuit boards used in the microelectronic industry.