Dielectric Studies of Segmental Dynamics in Epoxy Nanocomposites

Dielectric techniques were employed, along with differential scanning calorimetry (DSC), to investigate segmental dynamics associated with the glass transition in epoxy nanocomposites. Two epoxy network matrices were used, the first based on diglycidyl ether of Bisphenol A (DGEBA) and diethylenetriamine, and the second on DGEBA and poly(oxypropylene)diamine (Jeffamine D2000). In the first matrix, the inclusions were organically modified clays, diamond particles with a diameter of about 6 nm, and conductive carbon nanoparticles with a diameter of about 10 nm, whereas in the second, polyhedral oligomeric silsesquioxanes (POSS) were covalently attached to the chains as dangling blocks. In the nanocomposites of the first matrix, glassy at room temperature, segmental dynamics becomes slower and the glass transition temperature increases on addition of the filler. In the epoxy/POSS nanocomposites, rubbery at room temperature, dynamics is described by a two‐phase (layer) model: a fraction of the polymer is immobilized, obviously at interfaces with POSS, whereas the rest is slightly plasticized, compared to the pure matrix.