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

Materials

Nerea Sebastián¹  David Orencio López¹  Sergio Diez-Berart²  Mar໚ Rosario de la Fuente¹  Josep Salud²  Miguel Angel Pérez-Jubindo¹ 

[1] Departamento de Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, E-48080 Bilbao, Spain; E-Mails:;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; E-Mails:

关键词: liquid crystal dimers;    phase transitions;    critical exponents;    calorimetry;    dielectric spectroscopy;   

DOI  :  10.3390/ma4101632

来源: mdpi

【 摘 要 】

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 (N_B) phase, as they exhibit both molecular biaxiality and flexibility. According to the theory, the uniaxial nematic (N_U)–isotropic (I) phase transition is first-order in nature, whereas the N_B–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.

【 授权许可】

CC BY   
© 2011 by the authors; licensee MDPI, Basel, Switzerland.