Linear Viscoelasticity of the Direct Hexagonal Liquid Crystalline Phase for a Heptane/Nonionic Surfactant/Water System

Cordobés, F.; Muñoz, José; Gallegos, C.

doi:10.1006/jcis.1996.4707

Cited by 57 publications

(61 citation statements)

References 25 publications

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“…Mechanical and relaxation spectra (using the Generalized Maxwell model), along with creep compliance tests have been used by Cordobés et al (1996Cordobés et al ( , 1997 to illustrate the influence of the solubilization of a saturated hydrocarbon in the hexagonal mesophase formed by a nonionic surfactant in water. The addition of hydrocarbon yielded a wider plateau region, which was even larger as temperature went down.…”

Section: Hexagonal Liquid Crystals (H 1 ) (H 2 )mentioning

confidence: 99%

Rheological and phase behaviour of amphiphilic lipids

Muñoz

Alfaro

2000

Grasas y Aceites

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RESUMEN Comportamiento reológico y de fase de lípidos anfifílicosEn este capítulo se realiza una revisión de las distintas estructuras coloidales de asociación que pueden formar los lípidos anfifílicos en estado líquido-cristalino y de sus correspondientes propiedades de flujo en cizalla. Se describe la estructura y comportamiento reológico de cristales líquidos termotrópicos, con énfasis en los de tipo esméctico, fases gel, y cristales líquidos liotrópicos: nemáticos, laminares, laminares diluidos, dispersiones de laminares, hexagonales y cúbicos. Se hace hincapié en la importancia de una buena caracterización reológica y reo-óptica de cara a sus aplicaciones prácticas, desarrollo de formulaciones y como una técnica útil para determinar diagramas de fases y detectar cambios de estructura. Se ha usado una metodología histórica para analizar la evolución de la caracterización reológica e identificación de las diferentes estructuras líquido-cristalinas y estructuras afines. La interpretación de comportamientos de flujo viscoso no newtonianos, fenómenos tixotrópicos y antitixotrópicos y de las propiedades viscoelásticas lineales, determinadas con ensayos dinámicos y de fluencia, y no lineales, descritas mediante la diferencia de esfuerzos normales y ensayos de relajación del esfuerzo, se basa en la interrelación microestructuracomportamiento reológico. La naturaleza policristalina de los cristales líquidos resulta ser muy sensible a la cizalla, debido al cambio de tamaño y orientación de los dominios líquido-cristalinos mientras fluyen. PALABRAS-CLAVE: Comportamiento de fase Comportamiento reológico Lípidos anfifílicos. SUMMARY Rheological and phase behaviour of amphiphilic lipidsThis chapter reviews the different association structures which are likely to be formed by amphiphilic lipids in the liquid-crystalline state and their corresponding shear flow properties. The structure and rheological behaviour of thermotropic liquid crystals, emphasizing the properties of smectic mesophases, and those of lyotropic liquid crystals such as: nematic, lamellar, diluted lamellar, lamellar dispersions, hexagonal and cubic mesophases are described. The importance of a comprehensive rheological characterisation, including rheo-optical techniques, is pointed out for their practical applications, development of formulations and as a useful technique to assist in the determination of phase diagrams. A historical approach has been used to discuss the evolving field of the rheology and structure identification of liquid crystals formed by amphiphilic lipids and surfactants. Non-Newtonian viscous shear flow, thixotropic and antithixotropic phenomena, linear viscoelastic properties -described by dynamic and creep compliance experiments-and non-linear viscoelastic properties -described by the difference of normal stresses and stress relaxation tests are interpreted on the basis of a microstructure-rheology relationship. The polycrystalline nature of liquid crystals turns out to be rather sensitive to shear due to the change of both size...

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Section: Hexagonal Liquid Crystals (H 1 ) (H 2 )mentioning

confidence: 99%

Rheological and phase behaviour of amphiphilic lipids

Muñoz

Alfaro

2000

Grasas y Aceites

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“…7 prove that the three liquid crystal systems are typical plastic fluids, which exhibit shear thinning property. The form of the above curves is the same as those in another reference [26] . (2) Measurements of the values of critical stress.…”

Section: Study Of the Rheological Propertiesmentioning

confidence: 79%

“…The purpose of the measurement is to determine the region of linear viscoelasticity and to estimate the critical stress σ c , at which the structures in the samples are destroyed. The higher the value of σ c , the stronger the ability of the system to resist shear stress [26] . The stress scanning for the three liquid crystal systems is illustrated in Fig.…”

Section: Study Of the Rheological Propertiesmentioning

confidence: 99%

“…The viscoelastic properties of the system by using the frequency scanning can be reviewed by the changing curves of the relaxation time τ s and the modulus. The linear viscoelasticity refers to that the response for the system stress or strain is only the function of time [26] . Maxwell model is an ideal model to reflect the linear viscoelastic properties [26] .…”

Section: Study Of the Rheological Propertiesmentioning

confidence: 99%

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Studies on the phase properties of lyotropic liquid crystals of Brij35/sodium oleate/oleic acid/water system: By means of polarizing microscope, SAXS, 2H-NMR and rheological methods

Xu²,

Zhang³

et al. 2006

SCI CHINA SER B

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The pseudo-quaternary phase diagram of Brij35/sodium oleate/oleic acid/water systems has been investigated, and the liquid crystal area has been identified, which covers about two thirds of the whole phase diagram. The liquid crystal structure and behavior have been also studied by using polarizing texture, small angle X-ray scattering, 2 H-NMR and rheometer etc. The result shows that when the composition of the system changes along the line of AA′ in this large liquid crystal region, the structural change is cubic→cubic/lamellar→lamellar→lamellar/hexagonal→hexagonal. Meanwhile, we made the first attempt of systematic study of the rheological properties of the above system. The lattice constants of cubic and hexagonal liquid crystals are 10.53 and 5.68 nm, respectively.

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“…Larutan berair dan tidak berair dari surfaktan [1,2,3,4] akan membentuk fasa kristal cair liotropik yang berbeda sebagai hasil interaksi di antara struktur asosiasi atau aggregasi misel. Fasa ini memiliki sifat yang statis dan dinamis terkait dengan keadaan kristal dan cairan.…”

Section: Pendahuluanunclassified

Kristal Cair Lamelar Dalam Sistem Air, Tetra Etilen Glikol Dodesil Eter, Dan Tembaga Nitrat

Amran¹

2015

J.Ris.Kim.

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The lamellar liquid crystal in water, tetraethyleneglycol dodecylether, and copper nitrate system has been investigated. The results which characterized using optical polarizing microscope and smallangle x-ray diffraction showed the stability of the liquid crystal region was 40% and 65% by weight of surfactant. The interlayer spacing of lamellar liquid crystal, with and without various concentrations of copper nitrate content, remained constant. Keywords : Lamellar liquid crystal, Tetraethylene glycol dodecylether, Copper nitrate, Optical polarizing microscope, Small-angle x ray diffraction PENDAHULUANLarutan berair dan tidak berair dari surfaktan [1,2,3,4] akan membentuk fasa kristal cair liotropik yang berbeda sebagai hasil interaksi di antara struktur asosiasi atau aggregasi misel. Fasa ini memiliki sifat yang statis dan dinamis terkait dengan keadaan kristal dan cairan. Pemahaman tentang struktur dan fasa dinamis dari fasa liotropik atau kristal cair adalah amat penting dari segi fandamental dan praktis, terutama berbagai aplikasinya dalam berbagai bidang, seperti detergen [5] , kosmetik [6] farmasi [7,8] , emulsi [9] . Selain itu, diagram fasa dari surfaktan non-ionik polioksietilen menunjukkan suatu rangkaian fasa kristal-cair liotropik yang berbeda [10,11,12] . Jenis struktur kristal cair yang terbentuk tergantung pada kulvatur yang diadopsi oleh interfasa di antara agregat dan pelarut di selilingnya. Fase lamelar, heksagonal dan kubik adalah fase yang umum dalam sistem ini. Fase liotropik lamelar, Lα, muncul pada konsentrasi yang cukup tinggi apabila interfasa cenderung menjadi planar, meskipun surfaktan dengan rantai hidrofobik yang muncul pada konsentrasi rendah. Fasa ini terdiri dari kristal dimensi-satu sederhana tersusun dari lapisan pengganti dari air dan bilayer surfaktan dengan karakteristik polikristal. METODOLOGIBahan kimia yang dipergunakan tanpa pemurnian lebih lanjut yaitu Macol LA4 (tetraetilglikol dodesileter, dari Mazer Chemicals), sikloheksana (100%, dari J. T. Baker). Asam nitrat (70% ACS certified, Baxter Healthcare Corp., Scientific Product Division) digunakan untuk memperoleh pH air = 1,30, dan Cu(NO)3.2,5H2O dari Fisher Scientific. Air yang digunakan adalah deionisasi dan disuling.Diagram fasa kristal cair lamelar dalam sistem air, surfaktan dan garam tembaga nitrat (Gambar 1) diperoleh dengan mengaduk campuran surfaktan dan larutan tembaga nitrat (0; 8,1; 16,1; 24,2; 32,3; 40,1; 48,4; dan 56,5% w/w). Diagram fasa ditentukan dengan observasi visual menggunakan Optical Polarizing Microscope, dan dikonfirmasikan dengan hasil difraksi dari small-angle x-ray diffraction (Siemens Crystalloflex 4) dengan Tennelec detector system (Model PSD 100). HASIL DAN PEMBAHASANDiagram fasa kristal cair lamelar dalam sistem air, surfaktan dan garam tembaga nitrat dengan konsentrasi yang tinggi dinyatakan dalam Gambar 1 [13] . Pada gambar terlihat bahwa stabilitas daerah kristal cair lamelar berada pada 40% sampai 65% berat surfaktan.

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Linear Viscoelasticity of the Direct Hexagonal Liquid Crystalline Phase for a Heptane/Nonionic Surfactant/Water System

Cited by 57 publications

References 25 publications

Rheological and phase behaviour of amphiphilic lipids

Rheological and phase behaviour of amphiphilic lipids

Studies on the phase properties of lyotropic liquid crystals of Brij35/sodium oleate/oleic acid/water system: By means of polarizing microscope, SAXS, 2H-NMR and rheological methods

Kristal Cair Lamelar Dalam Sistem Air, Tetra Etilen Glikol Dodesil Eter, Dan Tembaga Nitrat

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