Conductivity, NMR and crystallographic study of N,N,N,N-tetramethylammonium dicyanamide plastic crystal phases: an archetypal ambient temperature plastic electrolyte material

摘要: N,N,N,N-Tetramethylammonium dicyanamide (Me4NDCA) has been examined via differential scanning calorimetry (DSC), thermogravimetric analysis, conductivity, single crystal X-ray diffraction and 1H nuclear magnetic resonance (NMR) analyses, was found to be highly conductive in the solid state (σ=10−3 S cm−2 at 420 K) also exhibit unusual plastic behaviour. To investigate correlation between such behaviour occurrence of molecular rotations crystal, NMR second moment measurements are compared with calculated values predicted from structure. While DSC analysis indicates a number solid–solid transitions ambient temperatures, subsequent Me4N+ cation shows that variety rotational motions become active low (<240 states occur over range temperatures rather than sharp transition. Conductivity reveals 320 K conductivity increases by more six orders magnitude state, line transition diffusive other phase observed this temperature have no marked effect on conductivity. Conduction is therefore envisaged involve vacancy-diffusion model, involving vacancies.