Functional Fluoropolymers with Good Low-dielectric Properties and High Thermostability

Abstract

Fluoropolymers can be utilized as dielectric substrates to ensure signal transmission speed and quality in modern communication technology. However, conventional fluoropolymer materials such as polytetrafluoroethylene (PTFE) are constrained by limited thermal stability and inferior processability. In this paper, two monomers (DBA-FBCB and DBAF-FBCB) based on benzocyclobutene and fluorobenzene groups have been successfully synthesized via effective C-H bond activation and nucleophilic aromatic substitution reactions. The monomers were thermally cross-linked to fluoropolymers (p-DBA-FBCB and p-DBAF-FBCB). Those polymers exhibited superior thermal stability with a glass transition temperature (T_g) > 370 ℃, a 5% weight loss temperature (T_5d) higher than 430 ℃, and low coefficient of thermal expansion (CTE) of 60.9 ppm /℃ from 35 ℃ to 250 ℃. p-DBAF-FBCB displayed excellent dielectric properties with a low dielectric constant (D_k) of 2.51 and dielectric loss factor (tanδ) of 2.41×10^-3 at a high frequency of 5 GHz, as well as an average D_k of 2.45 with an average tanδ of 1.5×10^-3 at the frequency from 1 to 10 MHz. The results demonstrate that those fluoropolymers are promising candidates for low-dielectric substrates or packaging materials in high-frequency communications or microelectronics industries.