Polymers under extreme two-dimensional confinement: Poly(ethylene oxide) in graphite oxide

The confinement of poly(ethylene oxide) in graphite oxide is studied using a combination of diffraction, calorimetric, and spectroscopic methods. Polymer intercalation into subnanometer graphite oxide layers leads to the complete suppression of crystallization phenomena and dielectric alpha-relaxation processes, as well as a slowdown of beta-relaxation modes. For the first time, high-resolution inelastic neutron scattering shows that poly(ethylene oxide) under these extreme confinement conditions adopts a planar zig-zag conformation, in no way resembling the characteristic 7(2) helical structure of the bulk crystal. The neutron data also shows a strong suppression of the COC and OCC bending modes and a distinct broadening of C-O torsional bands.