Structure and dynamics of poly (ethylene oxide) confined in the interlayer space of graphite oxide

Abstract

Resumen del trabajo presentado al 7th International Discussion Meeting on Relaxations in Complex Systems: "New results, Directions and Opportunities", celebrado en Barcelona (España) del 21 al 26 de julio de 2013.We explore the effects of chain size on the structure and dynamics of poly(ethylene oxide) (PEO) confined in the interlayer space of graphite oxide (GO). To this end, a PEO series of increasing chain length have been studied by means of high-resolution inelastic neutron spectroscopy (INS) on the TOSCA spectrometer, ISIS, UK, and broad band dielectric spectroscopy (BDS). PEO chains are accommodated in a layer of thickness 3.0–3.4 Å characterized by planar zigzag (trans–trans–trans) conformations. Moreover, we observe a strong reduction of vibrational motions for the confined polymer phase, as clearly evidenced by the disappearance, shift, and/or broadening of mode-specific INS spectral features, as well as by the complete suppression of crystallization and glass transition. All of these effects are surprisingly insensitive to the length of the PEO chains. BDS experiments of confined PEO show two relaxations: the faster one is independent of the chain length in agreement with INS results, whereas the slower one is dependent on the chain length and it could be associated to interfacial effects, typical of heterogeneous systems.Peer Reviewe