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Braga W, Santos O, Kimura N, Simões M, Palangana A. Optical signals of uniaxial and biaxial cholesteric lyotropic phases. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.118894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Santos O, Reis D, Oliveira-Filho A, Oliveira C, Figueiredo Neto A. Structure and local order of lyotropic cholesteric calamitic phases: The effect of the chiral molecule. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.118097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Farinha A, Flores F, Sampaio A, Kimura N, Freire F. Phase transition detection in liquid crystal analysis by mathematical morphology. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.117015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Akpinar E, Uygur N, Ordu OD, Reis D, Neto AMF. Effect of the surfactant head-group size dependence of the dye-surfactant interactions on the lyotropic uniaxial to biaxial nematic phase transitions. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.115842] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Akpinar E, Topcu G, Reis D, Neto AMF. Effect of the anionic azo dye Sunset Yellow in lyotropic mixtures with uniaxial and biaxial nematic phases. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114010] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Akpinar E, Guner E, Demir-Ordu O, Neto AMF. Effect of head-group size of some tetradecylalkylammonium bromide surfactants on obtaining the lyotropic biaxial nematic phase. Eur Phys J E Soft Matter 2019; 42:44. [PMID: 30953218 DOI: 10.1140/epje/i2019-11806-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 03/07/2019] [Indexed: 06/09/2023]
Abstract
Lyotropic quaternary mixtures of some tetradecylalkylammonium bromide surfactants were prepared to examine the effect of the size of the surfactant head group on the stabilization of different lyotropic nematic phases. The lyotropic mixtures were prepared by the addition of the tetradecylalkylammonium bromides (TTAABr) in the mixture of NaBr/decanol (DeOH)/water. The uniaxial to biaxial nematic phase transitions were determined via laser conoscopy. Some micellization parameters such as critical micelle concentration, degree of counterion binding and micellization Gibbs energy were evaluated from the electrical conductivity measurements of diluted binary surfactants/water solutions. The results indicate that the head-group size of the surfactant molecules influences the amphiphilic molecular aggregate topology. Moreover, the effective area per surfactant head group is a key parameter on stabilizing the lyotropic biaxial nematic phase.
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Affiliation(s)
- Erol Akpinar
- Bolu Abant Izzet Baysal University, Faculty of Arts and Sciences, Department of Chemistry, Golkoy, 14030, Bolu, Turkey.
| | - Emre Guner
- Bolu Abant Izzet Baysal University, Faculty of Arts and Sciences, Department of Chemistry, Golkoy, 14030, Bolu, Turkey
| | - Oznur Demir-Ordu
- Bolu Abant Izzet Baysal University, Faculty of Arts and Sciences, Department of Chemistry, Golkoy, 14030, Bolu, Turkey
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Akpinar E, Figueiredo Neto A. Experimental Conditions for the Stabilization of the Lyotropic Biaxial Nematic Mesophase. Crystals 2019; 9:158. [DOI: 10.3390/cryst9030158] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Nematic phases are some of the most common phases among the lyotropic liquid crystalline structures. They have been widely investigated during last decades. In early studies, two uniaxial nematic phases (discotic, ND, and calamitic, NC) were identified. After the discovery of the third one, named biaxial nematic phase (NB) in 1980, however, some controversies in the stability of biaxial nematic phases began and still continue in the literature. From the theoretical point of view, the existence of a biaxial nematic phase is well established. This review aims to bring information about the historical development of those phases considering the early studies and then summarize the recent studies on how to stabilize different nematic phases from the experimental conditions, especially, choosing the suitable constituents of lyotropic mixtures.
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Querciagrossa L, Ricci M, Berardi R, Zannoni C. Can multi-biaxial mesogenic mixtures favour biaxial nematics? A computer simulation study. Phys Chem Chem Phys 2017; 19:2383-2391. [DOI: 10.1039/c6cp05117k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A mixture of mesogens with different anisotropies favours the biaxial nematic phase.
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Affiliation(s)
- Lara Querciagrossa
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
| | - Matteo Ricci
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
| | - Roberto Berardi
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
| | - Claudio Zannoni
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
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Akpinar E, Turkmen M, Canioz C, Martins Figueiredo Neto A. Role of kosmotrope-chaotrope interactions at micelle surfaces on the stabilization of lyotropic nematic phases. Eur Phys J E Soft Matter 2016; 39:107. [PMID: 27837348 DOI: 10.1140/epje/i2016-16107-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Accepted: 10/26/2016] [Indexed: 06/06/2023]
Abstract
Three lyotropic quaternary systems of ionic surfactants were prepared to investigate the role of kosmotrope-chaotrope interactions at the micelle surfaces on stabilizing the different nematic phases. The ionic surfactants were potassium laurate (KL), sodium dodecylsulfate (SDS) and tetradecyltrimethylammonium bromide (TDTMABr), where KL is a kosmotrope surfactant, and others are chaotrope. The first system consisted of KL/decanol (DeOH)/water/alkali sulfate and the second of SDS/DeOH/water/alkali sulfate. The third system was prepared by adding sodium salts of chaotropic or kosmotropic anions to the primary mixture of TDTMABr/DeOH/water, separately. The characteristic textures of discotic nematic (N D), biaxial nematic (N B) and calamitic nematic (N C) phases were identified under polarizing light microscope. Laser conoscopy was employed to determine the uniaxial-to-biaxial phase transitions. The kosmotrope-kosmotrope or chaotrope-chaotrope interactions between the head groups of the surfactants and the ions of the electrolytes led to the stabilization of the N D phase. On the other hand, kosmotrope-chaotrope interactions stabilize the N B and/or N C phases.
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Affiliation(s)
- Erol Akpinar
- Arts and Sciences Faculty, Department of Chemistry, Abant Izzet Baysal University, Golkoy, 14030, Bolu, Turkey.
| | - Meric Turkmen
- Arts and Sciences Faculty, Department of Chemistry, Abant Izzet Baysal University, Golkoy, 14030, Bolu, Turkey
| | - Cihan Canioz
- Arts and Sciences Faculty, Department of Chemistry, Abant Izzet Baysal University, Golkoy, 14030, Bolu, Turkey
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Braga W, Santos O, Luders D, Kimura N, Sampaio A, Simões M, Palangana A. Refractive index measurements in uniaxial and biaxial lyotropic nematic phases. J Mol Liq 2016. [DOI: 10.1016/j.molliq.2015.10.058] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Nascimento ES, Henriques EF, Vieira AP, Salinas SR. Maier-Saupe model for a mixture of uniaxial and biaxial molecules. Phys Rev E Stat Nonlin Soft Matter Phys 2015; 92:062503. [PMID: 26764707 DOI: 10.1103/physreve.92.062503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Indexed: 06/05/2023]
Abstract
We introduce shape variations in a liquid-crystalline system by considering an elementary Maier-Saupe lattice model for a mixture of uniaxial and biaxial molecules. Shape variables are treated in the annealed (thermalized) limit. We analyze the thermodynamic properties of this system in terms of temperature T, concentration c of intrinsically biaxial molecules, and a parameter Δ associated with the degree of biaxiality of the molecules. At the mean-field level, we use standard techniques of statistical mechanics to draw global phase diagrams, which are shown to display a rich structure, including uniaxial and biaxial nematic phases, a reentrant ordered region, and many distinct multicritical points. Also, we use the formalism to write an expansion of the free energy in order to make contact with the Landau-de Gennes theory of nematic phase transitions.
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Affiliation(s)
- E S Nascimento
- Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05314-970 São Paulo, SP, Brazil
| | - E F Henriques
- Instituto de Física e Matemática, Universidade Federal de Pelotas, Caixa Postal 354, 96010-900 Pelotas, RS, Brasil
| | - A P Vieira
- Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05314-970 São Paulo, SP, Brazil
| | - S R Salinas
- Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05314-970 São Paulo, SP, Brazil
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Akpinar E, Reis D, Figueiredo Neto AM. Anomalous Behavior in the Crossover between the Negative and Positive Biaxial Nematic Mesophases in a Lyotropic Liquid Crystal. Chemphyschem 2014; 15:1463-9. [DOI: 10.1002/cphc.201301003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 02/24/2014] [Indexed: 11/11/2022]
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Akpinar E, Giesselmann F, Acimis M. Contributions of intermicellar distance, micelle volume and screw angle to the temperature dependence of helical pitch in the intrinsic lyotropic cholesteric phases. J Mol Liq 2014. [DOI: 10.1016/j.molliq.2013.11.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
Thermotropic biaxial nematic phases seem to be rare, but biaxial smectic A phases less so. Here we use molecular field theory to study a simple two-parameter model, with one parameter promoting a biaxial phase and the second promoting smecticity. The theory combines the biaxial Maier-Saupe and McMillan models. We use alternatively the Sonnet-Virga-Durand (SVD) and geometric mean approximations (GMA) to characterize molecular biaxiality by a single parameter. For non-zero smecticity and biaxiality, the model always predicts a ground state biaxial smectic A phase. For a low degree of smectic order, the phase diagram is very rich, predicting uniaxial and biaxial nematic and smectic phases, with the addition of a variety of tricritical and tetracritical points. For higher degrees of smecticity, the region of stability of the biaxial nematic phase is restricted and eventually disappears, yielding to the biaxial smectic phase. Phase diagrams from the two alternative approximations for molecular biaxiality are similar, except inasmuch that SVD allows for a first-order isotropic-biaxial nematic transition, whereas GMA predicts a Landau point separating isotropic and biaxial nematic phases. We speculate that the rarity of thermotropic biaxial nematic phases is partly a consequence of the presence of stabler analogous smectic phases.
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Affiliation(s)
- T B T To
- School of Mathematics, University of Southampton, Southampton SO17 1BJ, United Kingdom
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Risi CLS, Figueiredo Neto AM, Akpinar E, Santos MBL. Dynamic light scattering and viscosity measurements in a ternary and quaternary discotic lyotropic nematic liquid crystal: tuning the backflow with salt. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 88:022506. [PMID: 24032855 DOI: 10.1103/physreve.88.022506] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 07/05/2013] [Indexed: 06/02/2023]
Abstract
Using a dynamic light scattering technique, we measure the damping rate of thermal fluctuations of the nematic director for the so-called disklike nematic N(D) phase of both the ternary lyotropic K-laurate-1-decanol-H(2)O system and the quaternary one of similar composition except for the addition of salt (K(2)SO(4)). By varying the scattering angle in suitable geometries and polarizations, we are able to measure the orientational diffusivities associated with the pure deformations of splay and twist. A previous study made in the N(D) phase of the same ternary system yielded a large deviation between the splay and twist diffusivities. The effect was then interpreted in terms of the anisotropy between their associated viscosities due to induced flows, or backflow. In the present work we observe a strong increase of the backflow as an effect of the added salt. In addition, we make auxiliary measurements of shear viscosity and magnetic instabilities, which help to characterize the effect of the salt in the orientational diffusivities as they are mixed quantities involving elastic constants and viscosity coefficients.
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Affiliation(s)
- C L S Risi
- Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05314-970 São Paulo, São Paulo, Brazil
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Reis D, Akpinar E, Figueiredo Neto AM. Effect of Alkyl Chain Length of Alcohols on Cholesteric Uniaxial to Cholesteric Biaxial Phase Transitions in a Potassium Laurate/Alcohol/Potassium Sulfate/Water/Brucine Lyotropic Mixture: Evidence of a First-Order Phase Transition. J Phys Chem B 2013; 117:942-8. [PMID: 23270561 DOI: 10.1021/jp310981d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dennys Reis
- Instituto de Física, Universidade de São Paulo, P.O. Box 66318, 05314-970,
São Paulo, São Paulo, Brazil
| | - Erol Akpinar
- Department of Chemistry, Arts
and Sciences Faculty, Abant Izzet Baysal University, P.O. Box 14280, Golkoy, Bolu, Turkey
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