Low dielectric constant nanoporous poly(methyl silsesquioxane) using poly(styrene-block-2-vinylpyridine) as a template

Low dielectric constant nanoporous poly(methyl silsesquioxane) (PMSSQ) was prepared through the templating of an amphiphilic block copolymer, poly(styrene-b-2-vinylpyridine) (PS-b-P2VP). The experimental and theoretical studies suggest that the intermolecular hydrogen bonding interaction is existed between the PMSSQ precursor and PS-b-P2VP. The result of modulated differential scanning calorimeter (MDSC) indicates the miscible hybrid of the PMSSQ precursor/PS-b-P2VP. The miscible hybrid and the narrow thermal decomposition of the PS-b-P2VP lead to nanopores in the prepared films from the results of transmission electronic microscopy (TEM), atomic force microscopy (AFM), and small angle X-ray scattering (SAXS). The effects of the loading ratio and the PS block volume ratio (f_PS: 0.74, 0.46 and 0.35) on the morphology and properties of the prepared nanoporous PMSSQ films were investigated. The AFM and TEM studies suggest that the uniform pore morphology should be prepared from a modest porogen loading level for the optimum intermolecular hydrogen bonding. The PS-b-P2VP with a smaller f_PS requires a higher loading level to obtain the uniform pores. The refractive index and dielectric constant of the prepared nanoporous films could be tuned by the loading ratio in the range of 1.361-1.139 and 2.359-1.509, respectively. However, both properties are independent of the f_PS. The prepared study demonstrates the control of the morphology and properties of the nanoporous films through the polymer structure.