IBroadband dielectric relaxation spectroscopy (DRS) and, in addition, thermally stimulated depolarization currents (TSDC), a dielectric technique in the temperature domain, and differential scanning calorimetry (DSC) were employed to investigate polymer dynamics and glass transition in rubbery epoxy networks prepared from diglycidyl ether of bisphenol A (DGEBA) and poly(oxypropylene)diamine (Jeffamine® D2000, molar mass 2000) and their hybrid nanocomposites with the stannoxane “Sn4” cluster. In the nanocomposites a fraction x of Jeffamine chains (x=0.10, 0.25, 0.50) was replaced by diamino-functionalized stannoxanne clusters having the same functionality (4). Jeffamine D2000 and, for comparison, Jeffamine® D400 were also investigated. Four relaxations, the secondary γ and β relaxations, the a relaxation associated with the glass transition and the normal mode (NM) relaxation related with the presence of a dipole moment component along the chain contour, were identified and analyzed in the network and the hybrids, all having their origin in Jeffamine. Due to crosslinking the relaxations slow down in the pure network as compared to Jeffamine D2000, in particular the cooperative α and NM relaxations. The results by the three techniques suggest, in agreement with each other, that the structure becomes more rigid in the hybrids, as compared to the pure network: the glass transition shifts by a few degrees to higher temperatures and the α relaxation slows down. The local, secondary γ and β relaxations, on the contrary seem unaffected. The hybrid with the highest stannoxane content (x=0.50) exhibits a peculiar behaviour with an extremely broad glass transition and significantly reduced dielectric response.

Keywords: rubbery epoxy network, stannoxane cluster, polymer dynamics, glass transition