Unusual Accelerated Molecular Relaxations of a Tin Fluorophosphate Glass/Polyamide 6 Hybrid Studied By Broadband Dielectric Spectroscopy

Phosphate glass (Pglass)/polymer hybrids are a relatively new class of materials that combine the advantages of classical polymer blends and composites without their disadvantages. In the case of highly interacting Pglass/polymer (i.e., polyamide 6) hybrids, counter-intuitive properties that are difficult to explain are often observed. To shed light into the origins of the special behavior of the hybrids, we investigated the molecular relaxation processes in the hybrids using broadband dielectric spectroscopy. The dielectric loss spectra were fitted with the Havriliak-Negami equation and the characteristic relaxation times of the hybrid and the pure components were observed. The temperature dependence of the characteristic relaxation times was described using either the Vogel-Fulcher-Tammann, for the alpha-relaxations, or an Arrhenius type equation, for the beta- and gamma-relaxations. The addition of Pglass greatly accelerated both the alpha- and beta-relaxations of the polyamide 6. However, the gamma-relaxation was found to be independent of Pglass composition. This suggests partial miscibility in the solid state, which was confirmed via NMR spectroscopy. The unexpected dramatic change in the beta-relaxation process in the 10 vol.% Pglass hybrid suggests that blending can change the local environment of polyamide 6 due to the nanoscale morphology of this system as confirmed by TEM and NMR. It is thought that the fraction of miscible Pglass disrupts the hydrogen bonding between polyamide 6 chains and thereby reduces coordinated, multiple chain motion. In turn, this produces a plasticization effect and possible modification of the polyamide 6\u27s crystalline structure in the Pglass/polyamide 6 hybrids. (c) 2007 Elsevier Ltd. All rights reserved