Strategy to achieve low-dielectric-constant for benzoxazine-phthalonitriles: introduction of 2,2'-bis[4-(4-Maleimidephen-oxy)phenyl)]propane by in-situ polymerization

With the escalating demand in the high-frequency and high-speed communication field, it is imperative to develop materials with low dielectric constants (Low-ɛ) that also exhibit high-temperature resistance. In this study, the thermosetting bifunctional benzoxazine-phthalonitrile with pendant allyl groups (Boz-ph) was modified by incorporating 2,2'-bis[4-(4-maleimidephen-oxy)phenyl]propane (BMI-80). Specifically, BMI-80 was reacted with the pendant allyl groups of Boz-ph through in-situ polymerization, resulting in the synthesis of a series of high-performance Boz-ph/BMI-80 resins. The effects of various Boz-ph/BMI-80 resin proportions on curing behavior, thermal stability, mechanical, and dielectric properties were examined. With the introduction of BMI-80, the microstructure of the cured Boz-ph/BMI-80 resins transitioned from brittle to ductile fracture. The flexural strength of Boz-ph/BMI-80–100% reached a maximum of 102.8 MPa, compared to 70.1 MPa for pure Boz-ph. Additionally, the Boz-ph/BMI-80 resins displayed a high glass transition temperature (T_g = 325 ~ 333 ℃), low water absorption (less than 2.5%), and enhanced dielectric properties. Improvements in dielectric properties were observed with increases in BMI-80 content; the dielectric constant and dielectric loss of Boz-ph/BMI-80–100% were 3.31 and 0.008 (at 10 MHz), respectively. This study suggests that Boz-ph/BMI-80 resins have significant potential for use as matrices in high-temperature, high-frequency copper-clad laminates.