Showing papers by "Josep Salud published in 2009"
TL;DR: An exhaustive analysis of the critical behavior of the nematic to isotropic (N-to-I) phase transition on the liquid crystal hexyloxycyanobiphenyl (6OCB) has been performed and some discrepancies have been observed for the dielectric data in relation to such a scaling relationship.
Abstract: An exhaustive analysis of the critical behavior of the nematic to isotropic (N-to-I) phase transition on the liquid crystal hexyloxycyanobiphenyl (6OCB) has been performed. To do so, the accurate evolution of various physical magnitudes (static dielectric permittivity data together with specific heat and volumetric determinations) around the N-to-I transition has been required. The specific heat data with the isobaric thermal expansion coefficient and the derivative of the static dielectric permittivity with temperature have been proven to be related to each other by a scaling relationship. However, some discrepancies have been observed for the dielectric data in relation to such a scaling relationship and the critical behavior of the N-to-I phase transition. All information has been used to get some insight on the strength of the first-order N-to-I phase transition of the 6OCB in relation to the other counterparts in the nOCB series of compounds.
17 citations
TL;DR: In this paper, the stable solid polymorphism of cycloheptanol (C 7 H 14 O, for short C 7 -OH) is revised and four solid stable phases, denoted on cooling from the liquid as phases I, II, III and IV are identified from X-ray diffraction measurements.
Abstract: The stable solid polymorphism of cycloheptanol (C 7 H 14 O, 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.
5 citations