A new mechanism for the low dielectric property of POSS nanocomposites: the key role of interfacial effect

The low dielectric constant (epsilon) of polyhedral oligomeric silsesquioxanes (POSS) was generally attributed to its porous structure. In this work, we propose a new mechanism for the low epsilon of the POSS-based nanocomposites from the interfacial effect point of view. The investigation on a typical nanocomposite, polystyrene/POSS, found that POSS molecules take crystallization to form crystalline nanoplatelets (PCPs) in PS. Correspondingly, the dielectric constant can be reduced to around 2.30. A detailed investigation excluded the possible influence of the chain stacking and chain mobility of the polymers on epsilon. It was demonstrated, for the first time, that the epsilon shows a high correlation with interface area which is reflected by a rigid amorphous fraction (RAF), thus revealing the key role of the interfacial effect on reducing the low dielectric constant.