Piers-Rubinsztajn reaction for BCB functionalized silphenylene/silbiphenylene siloxane oligomers to highly crosslinked low-k thermosets

Abstract

Herein, we have successfully prepared two benzocyclobutene (BCB) functionalized siloxane oligomers (PhBVSi and BPBVSi) by Piers-Rubinsztajn reaction, which provides a facile method for the post-curable silphenylene or silbiphenylene-containing siloxane oligomers. These oligomers can be cured above 200 °C to prepare the highly crosslinked thermosets. Due to the introduction of silphenylene and silbiphenylene units and the highly crosslinked structure from BCB, the thermosets exhibit high initial storage modulus and good thermostability (Td5 > 490 °C in nitrogen). Tan δ curve of the cured PhBVSi and BPBVSi appears peaks with small dissipation factor of 0.05 at 134 °C and 148 °C, respectively, which refers to unconventional glass transition proved by the penetration mode TMA. In addition, both thermosets show well dielectric property with low dielectric constants (<2.8) and low dissipation factor (<0.001) at 1 MHz. The facile preparation process by P-R reaction will provide an alternative new route for other post curable polymers especially siloxane polymers.