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Materials 2011, 4(10), 1632-1647; doi:10.3390/ma4101632

Effect of Molecular Flexibility on the Nematic-to-Isotropic Phase Transition for Highly Biaxial Molecular Non-Symmetric Liquid Crystal Dimers

1
Departamento de Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, E-48080 Bilbao, Spain
2
Grup de Propietas Físiques dels Materials (GRPFM), Departament de Física i Enginyeria Nuclear, E.T.S.E.I.B., Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain
3
Departamento de Química Orgánica, Facultad de Ciencias-ICMA, Universidad de Zaragoza, E-50009 Zaragoza, Spain
*
Author to whom correspondence should be addressed.
Received: 22 August 2011 / Revised: 2 September 2011 / Accepted: 19 September 2011 / Published: 27 September 2011
(This article belongs to the Special Issue Liquid Crystals 2011)
View Full-Text   |   Download PDF [1102 KB, 28 September 2011; original version 27 September 2011]   |  

Abstract

In this work, a study of the nematic (N)–isotropic (I) phase transition has been made in a series of odd non-symmetric liquid crystal dimers, the α-(4-cyanobiphenyl-4’-yloxy)-ω-(1-pyrenimine-benzylidene-4’-oxy) alkanes, by means of accurate calorimetric and dielectric measurements. These materials are potential candidates to present the elusive biaxial nematic (NB) phase, as they exhibit both molecular biaxiality and flexibility. According to the theory, the uniaxial nematic (NU)–isotropic (I) phase transition is first-order in nature, whereas the NB–I phase transition is second-order. Thus, a fine analysis of the critical behavior of the N–I phase transition would allow us to determine the presence or not of the biaxial nematic phase and understand how the molecular biaxiality and flexibility of these compounds influences the critical behavior of the N–I phase transition.
Keywords: liquid crystal dimers; phase transitions; critical exponents; calorimetry; dielectric spectroscopy liquid crystal dimers; phase transitions; critical exponents; calorimetry; dielectric spectroscopy
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MDPI and ACS Style

Sebastián, N.; López, D.O.; Diez-Berart, S.; de la Fuente, M.R.; Salud, J.; Pérez-Jubindo, M.A.; Ros, M.B. Effect of Molecular Flexibility on the Nematic-to-Isotropic Phase Transition for Highly Biaxial Molecular Non-Symmetric Liquid Crystal Dimers. Materials 2011, 4, 1632-1647.

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