Reentrant isotropic-calamitic nematic phase transition in potassium laurate-decanol- D2O mixtures

Abstract

The phase diagram is an interesting field of research, particularly in lyotropic liquid crystals (LLC). In this way, one of the most important phase diagrams of this LLC system was reported by Yu and Saupe. Two uniaxial (calamitic--N(C) and discotic--N(D)) and one biaxial nematic (N(B)) phases were determined by these authors. Furthermore, in this phase diagram the classical isotropic phase (I was observed at high temperature as well as a reentrant isotropic phase (I(RE)) which takes place at lower temperature. Later, this phase diagram was also studied by several authors and in all cases the I(RE)-N(C)-I phase transitions were not observed. In this work, we present a study of this phase diagram through digital image processing and refractometry optical techniques. The occurrence of these phase transitions is investigated and characterized. In addition, the order parameter is obtained based on the Vuks hypothesis from a particular point, in the range of the N(C) phase, where the absolute value of the optical birefringence (Deltan is maximum.

Properties of the broad-range nematic phase of a laterally linked H-shaped liquid crystal dimer

“…b N was first identified by Yu and Saupe in a lyotropic mixture of potassium laurate / 1-decanol / water system. [17] Although the biaxial order has been observed by other researchers in this and other lyotropic nematics, [18][19][20][21][22][23][24][25][26][27] the issue remains controversial, as the studies by Berejnov et al [28,29] suggest that the biaxial order is only transient.…”

Pressure-driven reentrant phenomena in liquid crystals: the role of inverse layer spacing

“…From the expressions of the N-S A transition temperature, Equation (13), and the 'inverse layer spacing', Equation (7), in addition to the above experimental observations [22,23,25], it is obvious that the coupling parameters e 1 , b 1 and b 2 are pressure dependent. This makes the renormalised metastable temperature T 0 AN and the effective couplings and l eff also pressure dependent.…”

“…The phenomenon of reentrant phase transition, that is an occurrence of a low symmetric phase in between two high symmetric phases, is intrinsically novel and the sustained interest in this problem is underlined by its discovery in amazingly diverse classes of condensed matter systems [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. In achiral liquid crystals, the nematic (N)-partial bilayer smectic A ðS A d Þ-reentrant nematic (N R )-monolayer smectic A ðS A 1 Þ phase sequence was first reported by Cladis [18] in a mixture of {p-[p-hexyloxybenzylidene-amino] benzonitrile} (HBAB) and [N-p-cyanobenzylidene-pn-octyloxyaniline] (CBOOA).…”

Determination of order parameter and birefringence depending on temperature of nematic calamitic mesophase formed by TTAB + water binary system using polarized microscopy

“…These properties are governed by the order parameter [10]. Thus, the study of the order parameter of lyotropics has accelerated in recent years [11][12][13].…”