Papers by Keyword: Relaxation Times

Abstract: Solid-state nuclear magnetic resonance (NMR) spectroscopy has emerged as a relatively facile technique for the characterization of multi-component polymer systems. In particular, it has emerged to be a useful technique for probing the molecular structure, conformation and dynamics of polymer chains at interfaces between phases in various types of multi-component polymer systems including nanomaterials. The usefulness of solid-state NMR stems from its ability to non-destructively probe not only the bulk of the polymer, but moreover its ability to selectively probe the interface or interphase. As such, the technique has been extensively exploited in the study of multi-component polymer systems. To achieve ¹³C spectral resolution in the solid-state magic angle spinning (MAS), dipolar decoupling and cross-polarization are applied which enables the study of individual carbon atoms directly with excellent resolution and sensitivity. Some examples of applications of this technique to the study of multiphase aliphatic polyesters are reviewed herein.

Abstract: A gel electrolyte system was prepared by dissolving poly(methyl methacrylate) in ethylene carbonate and propylene carbonate doped with salicylic acid and plasticized with dibutylphthalate (DBP). The gel was heated to 70 0C before it was cast into glass dishes. The composition of the electrolytes was 35 wt% EC, 30 wt% PC, 5 wt% SA, 5wt% DBP and 25 wt% PMMA. The gel electrolyte was sandwiched between two stainless-steel blocking electrodes and impedance measurements were conducted. The conductivity of the gel electrolyte was 2.03 x 10-4 S cm-1 at room temperature. The conductivity activation energy was obtained from the log σ versus 103/T graph. Loss tangent was calculated at every frequency for all temperatures. From the tan δ versus frequency plot, the activation energy of relaxation of the ion was calculated and plotted as ln τ versus 103/T. The conductivity activation energy value was (0.21 ± 0.04) eV and the activation energy of relaxation was (0.24±0.07) eV. The similarity between these activation energies imply that the protons ‘hop’ from one electronegative oxygen site in DBP to another.