A novel post-polymerizable polynorbornene prepared via ROMP: easy synthesis and conversion into a free-standing film with high Tg and low dielectric constant

Abstract

A novel linear silicon-containing polynorbornene (BCB-PNB, M_n = 93 000 g mol⁻¹) with thermo-crosslinkable benzocyclobutene side chains was synthesized through ring-opening metathesis polymerization (ROMP). This polymer displayed good solubility and film-forming ability. After post-polymerization at high temperature, a free-standing film based on BCB-PNB was easily converted to a crosslinked network, which exhibited a dielectric constant of 2.60 for frequencies ranging from 40 Hz to 30 MHz. In particular, this crosslinked film exhibited a high T_g of up to 400 °C, which was much higher than that of the previously reported polynorbornenes prepared by ROMP. This is the first example of a polynorbornene prepared by ROMP with such a high T_g and good processability. Besides, the crosslinked film also displayed high hydrophobicity. These results indicate that the introduction of thermo-crosslinkable benzocyclobutene groups into polynorbornene side chains can greatly enhance the properties of the polymers. This work also develops a facile method for the preparation of a new free-standing post-polymerizable polynorbornene film.