Mechanism of Dielectric Constant Variation of POSS-Based Organic−Inorganic Molecular Hybrids

Three series of POSS containing organic−inorganic molecular hybrid low dielectric materials with different molecular architectures were prepared, in which isobutylstyryl-polyhedral oligomeric silsesquioxane (IBS-POSS) and octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) were adopted as an inorganic core to construct the pendant-type PAS-POSS pendt and star-type PAS-POSS star hybrids, respectively. Among the organic−inorganic molecular hybrids, the POSS contents range from 0.65, 1.36, 1.62, to 3.14 in molar percentage (mol %) in PAS-POSS pendt hybrids, and from 0.36, 1.37, 2.06, to 3.72 in molar percentage (mol %) in PAS-POSS star hybrids. Different polar organic components (organic polymeric chains) including PS, PAS, and PMMA were build into the star-type hybrids. The analysis on the relationship between molecular structure of these hybrids and their dielectric constants indicates that the incorporation of POSS molecules into the polymer matrixes will lower the dielectric constant ( k ) of the resulted hybrids (both pendant-type and star-type). At the same POSS content, the star-type hybrids possess a lower k than those of pendant-type ones, which is mainly assigned to the larger free volume resulted from star-type hybrids. Simultaneously, it is found that the dielectric constant of the resulting hybrids increases with the polarity of organic polymeric chain when possessing the similar molecular structure and POSS content.