An Intrinsically Microporous Network Polymer with Good Dielectric Properties at High Frequency

Abstract

An intrinsically microporous fluoropolymer has been successfully synthesized through thermo-cross-linking of a functional monomer having a quaternary carbon center and thermopolymerizable trifluorovinyl ether groups as the side chains. Because the monomer has a tetrahedral configuration, the thermo-cross-linking produces spontaneously formed micropores with an average size of 8 Å in the polymer. Because of the existence of the micropores, the fluoropolymer exhibits excellent dielectric properties with dielectric constant (Dk) of 2.36 and dissipation factor (Df) of 1.29 × 10–3 at a frequency of 5 GHz. Moreover, the polymer shows very low water uptake (<0.08% in water of 99 °C for 72 h) and high transparency (transmittance of 93% varying from 400 to 1100 nm). TGA and DMA data show that the polymer has 5 wt % loss temperature of 492 °C (in N2) and Young’s modulus of 4.95 GPa, respectively. These results suggest that the polymer is very suitable as the matrix resin for the production of the composites utilized in high-frequency printed circuit boards (HF-PCBs). In particular, this work is the first example for the production of a low Dk and Df polymer using a strategy of spontaneously forming pores. Because HF-PCBs have a broad range of applications, this contribution is of considerable industrial importance.