A new type of unsaturated polyester resin with low dielectric constant and high thermostability: Preparation and properties

A new type of unsaturated polyester resins (UP) with low dielectric constant (κ) and high thermostability was prepared by doping N-phenylmaleimides containing perfluoroalkyl substituents (-CF₃ and -C₆F₁₃) into a commercial unsaturated polyester resin. In comparison with neat UP resin, the doped UP resins showed decreased dielectric constant and increased char yields. The best result was obtained when the substituent was -CF₃, which gave a dielectric constant of 3.63 and 5 wt%, loss temperature of 336 °C with a char yield of 5.57% under N ₂. Such data are superior to those of neat UP resin, which showed dielectric constants of 4.38 and 5 wt%, a loss temperature of 327 °C with a char yield of 2.25%. In this contribution, a new environmentally-friendly procedure for the synthesis of the fluoro-containing maleimides was also provided, in which a Bronsted acidic room temperature ionic liquid was employed as a catalyst and the products were obtained through merely decanting and removal of the solvent.