Calorimetric study of thiophene from 13 to 300 K. Emergence of two glassy crystalline states

• Published in: The Journal of chemical thermodynamics 1985, Vol.17 (10), p.949-966
• Main Authors: Figuière, Pierre, Szwarc, Henri, Oguni, Masaharu, Suga, Hiroshi
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Physics; Structure of solids and liquids; crystallography
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/0021-9614(85)90008-4

Heat capacities of stable and metastable phases of thiophene crystal were measured in the 13 to 300 K temperature range with an on-line automated adiabatic calorimeter. The enthalpies and entropies of the transitions and fusion that occurred at the following temperatures were measured: ▪ The condition of existence and the precise temperature of the II 2-to-II 1 phase transition were found. A glass-transitional behaviour was observed around 42 K for the stable V phase and around 37 K for the metastable II 2 phase. Thermodynamic properties in the crystal and liquid states were calculated from our calorimetric results. Comparison of the calorimetric entropy with the spectroscopic value shows that the stable V phase has a residual entropy of (1.25 ± 0.9) J·K −1·mol −1 and the metastable II 2 phase one of (1.48 ± 0.9) J·K −1·mol −1. Thus, both stable and metastable phases of thiophene crystal provide new examples of glassy crystals.