Solid phases in cycloheptanol: Dynamic disorder and glass transitions

• Published in: Journal of non-crystalline solids Vol. 355; no. 52; pp. 2550 - 2556
• Main Authors: Salud, J., López, D.O., Diez-Berart, S., Pérez-Jubindo, M.A., de la Fuente, M.R., Rute, M.A., Puertas, R.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 15-12-2009; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Dielectric properties; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electric modulus; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Fragility; Glass transition; Glass transitions; Permittivity (dielectric function); Physics; Relaxation; Specific phase transitions; X-ray diffraction; Glass transition; Relaxation; 64.70kj; Dielectric properties; X-ray diffraction; 61.05cp; Electric modulus; 77.22; 64.70p; Fragility; Cooling; XRD; Glass formation; Specific heat; Complex permittivity; Permittivity; Conformation; Polymorphism
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2009.09.007

The stable solid polymorphism of cycloheptanol (C
7H
14O, for short C
7–OH) is revised in the present paper. Four solid stable phases, denoted on cooling from the liquid as phases I, II, III and IV are identified from X-ray diffraction measurements. Lattice symmetry of phase III has been unambiguously stated as orthorhombic. Diffraction patterns corresponding to phase IV have been also indexed as orthorhombic, but only in a tentative way. A detailed broadband dielectric spectroscopy study devoted to these phases has been made. Such an experimental technique has no revealed differences between phases III and IV and from specific-heat measurements, the III–IV phase transition has not been observed yet. Dielectric results seem to evidence that the dynamic disorder of phase III and/or IV should be intra-molecular attributed to changes between the possible distinguishable molecular conformations along with possible hydroxyl group rotations. The possibility of C
7–OH as
conformational glass-
forming material is discussed.