Chain Dimension and Dynamics of Polymers in Well-Defined Non-sticky Nanocomposites of Molecular Nanoparticle Polyhedral Oligomeric Silsesquioxane/Poly(butylene oxide)

摘要

The chain dimension and dynamics of type-A polymer, poly(1, 2-butylene oxide) (PBO), in the nanocomposites comprising polyhedral oligomeric silsesquioxane (POSS) nanoparticles have been investigated in broad frequency and temperature windows by utilizing broadband dielectric spectroscopy and rheology. Non-crystalline and dielectric "invisible" molecular nanoparticle POSS was specially designed to ensure its miscibility with the PBO matrix, which was verified by quantitative estimation of solubility parameters and subsequent X-ray scattering experiments. Dispersions of POSS in the PBO matrix up to 10 vol % have been investigated. Dielectric experiments revealed a negligible change of the dielectric relaxation strength of the normal mode and thus the statistical chain dimension of PBO, regardless of the POSS loadings and the polymer chain lengths spanning from the unentangled to the entangled region. The introduction of nanoparticles is found to influence both the chain and segment dynamics when the molecular weight of the polymer is relatively low. However, by renormalized with the segmental relaxation, the dielectric chain relaxation shows identical characteristic relaxation time with that of the neat polymer, independent of the volume fractions of POSS, which is consistent with the terminal relaxation time determined in the rheology experiments. The slowing down of segmental relaxation has been attributed to the influence of nanoparticles on the chain ends associated with excess free volume. The possible confinement, solvent, and filler effects in this type of a non-sticky nanocomposite model system have been further discussed.