Preparation of nanoporous poly(methyl silsesquioxane) films using core-shell silsesquioxane as porogen

Abstract

Nanoporous poly(methyl silsesquioxane) (PMSSQ) thin films were successfully prepared using a new thermally sacrificing porogen, dimethylamino-functionalized polyhedral oligomeric silsesquioxane (DMA-POSS). The core-shell silsesquioxane was synthesized from Acrylo POSS with 3-dimethylaminopropylamine (DMAPA) and 2-dimethylamino ethyl acrylate (DMAEA) using Michael addition reaction. Miscible hybrid materials were obtained through strong hydrogen-bonding interaction between the Si–OH end group in MSSQ and the tertiary amino groups in DMA-POSS. Nanopores in PMSSQ matrix were generated by thermal decomposing DMA-POSS at 425 °C. The AFM and FESEM studies suggested that nanopores were homogeneously distributed in the prepared thin films. As the porosity increased up to 16.4%, the refractive index and the dielectric constant of the nanoporous films were decreased from 1.379 to 1.307 and 2.8–2.2, respectively. The tertiary amino substitutes could promote the silanol condensation and improve the mechanical properties. Therefore, the hardness retained around 1 GPa as the porosity increased. The low-dielectric constant, good thermal and mechanical property suggested the potential applications of these films as low-dielectric constant materials.