Dynamics of Multifunctional Polyhedral Oligomeric Silsesquioxane/Poly(propylene oxide) Nanocomposites As Studied by Dielectric Relaxation Spectroscopy and Dynamic Mechanical Spectroscopy

An investigation was carried out of the segmental and normal mode dynamics in multifunctional polyhedral oligomeric silsesquioxane (POSS)/poly(propylene oxide) (PPO) nanocomposites. Data were generated by broadband dielectric relaxation spectroscopy (DRS) and dynamic mechanical spectroscopy (DMS) over a wide range of frequency and temperature. Neat PPO exhibits two relaxation processes:  normal mode (αN) and segmental mode (α). The two multifunctional POSS reagents utilized (octaglycidyldimethylsilyl-POSS and octaepoxycyclohexyldimethylsilyl-POSS) show a segmental process at lower frequency and a local relaxation at higher frequency. The POSS/PPO nanocomposites also show two relaxation processes (αN and α), but interestingly, their time scale is shorter than in the corresponding neat PPO. Molecular origin and spectral characteristics of all relaxations are described. Comparison of DRS and DMS results revealed identical trends with respect to the POSS concentration, temperature, and the same time scale for...