Economical bisphenol-based dibenzocyclobutene resins with excellent thermal and dielectric properties for high-frequency communication applications.

Benzocyclobutene (BCB) resins have recently gained significant attention as dielectric materials, yet most suffer from high costs. Herein, five economical bisphenol-based dibenzocyclobutene resins (BCB-A, BCB-AF, BCB-F, BCB-B and BCB-O) were readily synthesized from 4-bromobenzocyclobutene and commercial bisphenols via an Ullmann reaction. Upon thermal curing, the corresponding crosslinked polymers were obtained. All cured BCB resins exhibited high glass transition temperature (T g) values of 287-329 °C, excellent thermal stability with 5% weight loss temperatures (T 5%) of 408-445 °C, and CTE values as low as 23.8 ppm °C-1. The cured resins also exhibited good flexural properties, with flexural strengths of 63.7-98.4 MPa and flexural moduli of 2.2-2.7 GPa. Notably, they also demonstrated favorable high-frequency dielectric properties at 10 GHz, with dielectric constant (D k) values of 2.54-2.83 and dissipation factor (D f) values of 2.32 × 10-3 to 3.63 × 10-3. Considering the low cost of bisphenols, the facile Ullmann reaction and the good overall performance, these bisphenol-based dibenzocyclobutene resins are promising candidates for high-frequency communication applications.