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Cosima Stubenrauch - One of the best experts on this subject based on the ideXlab platform.
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tuning gelled lyotropic liquid crystals llcs probing the influence of different low molecular weight gelators on the phase diagram of the system h2o nacl genapol la070
Soft Matter, 2019Co-Authors: Katja Steck, Jan H Van Esch, David K Smith, Cosima StubenrauchAbstract:Gelled lyotropic liquid crystals (LLCs) are highly tunable multi-component materials. By studying a selection of low molecular weight gelators (LMWGs), we find gelators that form self-assembled gels in LLCs without influencing their phase boundaries. We studied the system H2O/NaCl-Genapol LA070 in the presence of (a) the organogelators 12-hydroxyoctadecanoic acid (12-HOA) and 1,3:2,4-dibenzylidene-d-sorbitol (DBS) and (b) the hydrogelators N,N'-dibenzoyl-l-cystine (DBC) and a tris-amido-cyclohexane derivative (HG1). Visual phase studies and oscillation shear frequency sweeps confirmed that 12-HOA acts as co-surfactant (stabilizing the lamellar Lα phase and destabilizing the hexagonal H1 phase), thus preventing gelation. Conversely, DBS was a potent gelator for LLCs, with the phase boundaries un-influenced by the presence of DBS; gelled lamellar Lα, and softly-gelled hexagonal H1 phases are formed. For the hydrogelator DBC, the LLC phase boundaries were only slightly altered, but no gelled LLCs were formed. For the hydrogelator HG1, however, the phase boundaries were unaffected while gelled lamellar Lα and softly-gelled hexagonal H1 phases were formed. Temperature-dependent rheology measurements demonstrated that by changing the DBS or the HG1 concentration, the sol-gel transition temperature of the gelled lamellar Lα phase can be adjusted such that (a) Tsol-gel is below the Lα-isotropic phase transition (DBS, HG1 mass fraction η = 0.0075) and (b) Tsol-gel is above the gelled Lα-isotropic phase transition (DBS, HG1 η = 0.015). This opens the possibility of temporal materials control by addressing phase transitions in different orders. As this system contains oil and water, both the organogelator DBS and the hydrogelator HG1 can gel these LLCs, but this clearly does not apply to all organogelators/hydrogelators. The study indicates that careful optimization of LMWGs is required to avoid interaction with the surfactant layer and to optimize the Tsol-gel value, which is important for the application of LMWGs in gelled LLCs.
Katja Steck - One of the best experts on this subject based on the ideXlab platform.
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tuning gelled lyotropic liquid crystals llcs probing the influence of different low molecular weight gelators on the phase diagram of the system h2o nacl genapol la070
Soft Matter, 2019Co-Authors: Katja Steck, Jan H Van Esch, David K Smith, Cosima StubenrauchAbstract:Gelled lyotropic liquid crystals (LLCs) are highly tunable multi-component materials. By studying a selection of low molecular weight gelators (LMWGs), we find gelators that form self-assembled gels in LLCs without influencing their phase boundaries. We studied the system H2O/NaCl-Genapol LA070 in the presence of (a) the organogelators 12-hydroxyoctadecanoic acid (12-HOA) and 1,3:2,4-dibenzylidene-d-sorbitol (DBS) and (b) the hydrogelators N,N'-dibenzoyl-l-cystine (DBC) and a tris-amido-cyclohexane derivative (HG1). Visual phase studies and oscillation shear frequency sweeps confirmed that 12-HOA acts as co-surfactant (stabilizing the lamellar Lα phase and destabilizing the hexagonal H1 phase), thus preventing gelation. Conversely, DBS was a potent gelator for LLCs, with the phase boundaries un-influenced by the presence of DBS; gelled lamellar Lα, and softly-gelled hexagonal H1 phases are formed. For the hydrogelator DBC, the LLC phase boundaries were only slightly altered, but no gelled LLCs were formed. For the hydrogelator HG1, however, the phase boundaries were unaffected while gelled lamellar Lα and softly-gelled hexagonal H1 phases were formed. Temperature-dependent rheology measurements demonstrated that by changing the DBS or the HG1 concentration, the sol-gel transition temperature of the gelled lamellar Lα phase can be adjusted such that (a) Tsol-gel is below the Lα-isotropic phase transition (DBS, HG1 mass fraction η = 0.0075) and (b) Tsol-gel is above the gelled Lα-isotropic phase transition (DBS, HG1 η = 0.015). This opens the possibility of temporal materials control by addressing phase transitions in different orders. As this system contains oil and water, both the organogelator DBS and the hydrogelator HG1 can gel these LLCs, but this clearly does not apply to all organogelators/hydrogelators. The study indicates that careful optimization of LMWGs is required to avoid interaction with the surfactant layer and to optimize the Tsol-gel value, which is important for the application of LMWGs in gelled LLCs.
Frank Giesselmann - One of the best experts on this subject based on the ideXlab platform.
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gelation of lyotropic liquid crystal phases the interplay between liquid crystalline order and physical gel formation
Langmuir, 2019Co-Authors: Sonja Dieterich, Thomas Sottmann, Frank GiesselmannAbstract:We present a systematical investigation of gelled lyotropic liquid crystals (LLCs). This new class of soft materials combines the anisotropy of LLCs with the mechanical stability of a physical gel. The studied LLC system consists of sodium dodecyl sulfate as a surfactant, n-decanol as a cosurfactant, and water as a solvent. At room temperature, four liquid crystalline phases (lamellar Lα, nematic Nd and Nc, and hexagonal H1) are formed depending on the composition. We were successful in gelling the lyotropic lamellar phase with the low-molecular-weight organogelator 12-hydroxyoctadecanoic acid (12-HOA). The obtained gelled lamellar phase shows optical birefringence, elastic response, and no macroscopic flow. However, we were not able to obtain gels with hexagonal or nematic structure. These findings can be explained twofold. When gelling the hexagonal phase, the long-range hexagonal order was destroyed and an isotropic gel was formed. The reason might be the incompatibility between the gel fiber network and the two-dimensional long-range translational order of the cylindrical micelles in the hexagonal phase. Otherwise, the lyotropic nematic phase was transformed into an anisotropic gel with the lamellar structure during gelation. Evidently, the addition of the gelator 12-HOA to the lyotropic system considerably widens the lamellar regime because the integration of the surface-active 12-HOA gelator molecules into the nematic micelles flattens out the micelle curvature. We further investigated the successfully gelated Lα phase to examine the impacts of the gel network and the remaining monomeric gelator on both the structure and properties of the gelled lamellar phase. Small-angle X-ray scattering results showed an arrested lamellar layer spacing in the gelled state, which indicates a higher translational order for the gelled lamellar phases in comparison with their gelator-free counterparts.
Jhon Fredy Betancur Perez - One of the best experts on this subject based on the ideXlab platform.
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uso alternativo del colorante GelRed en la tincion de acidos nucleicos alternative use of GelRed dye in the staining nucleic acids
Archivos De Medicina, 2013Co-Authors: Nestor Javier Orozco Clavijo, Jhoan Camilo Herrera Canon, Jhon Fredy Betancur PerezAbstract:Objetivo: Determinar la reproducibilidad en la tincion del ADN en geles de agarosa mediante el colorante GelRedTM con el fin de reemplazar el uso del bromuro de etidio en la tincion de acidos nucleicos. Materiales y Metodos: Se realizo extraccion de ADN total de sangre periferica a nueve muestras de pacientes con cancer colorrectal, posteriormente se amplifico un fragmento de ADN de 494 pb asociado al exon 15 del gen APC y de seis fragmentos entre 150 pb y 350 pb asociados a los genes hMLH-1 y MSH-2; ambas preparaciones, ADN total y ADN amplificado fueron visualizadas mediante el uso del colorante GelRed y Bromuro de Etidio. Resultados: El uso del colorante GelRed para la tincion de acidos nucleicos (ADN) permitio visualizarlos de forma eficiente. Conclusion: El reactivo GelRed es altamente reproducible y se recomienda usarlo incluido en las muestras de ADN, para disminuir la contaminacion en los laboratorios de biologia molecular. Objetive: Determine the reproducibility of DNA staining in agarose gels using the dyeGelRedTM in order to replace ethidium bromide in the use of nucleic acids staining.Materials and Methods: The extraction of the total DNA from nine samples and theamplified DNA fragment of 494 pb of exon 15 associated with the APC gene from sixfragments between 150 pb – 350 pb associated with the hMLH-1 and MSH-2 geneswas performed. Both preparations, total DNA and amplified DNA were visualized usingGelRed and Ethidium bromide dye. Results: Both systems of coloration gave verysimilar results; the DNA can be visualized correctly without any difficulty. Conclusion:The GelRed dye is highly reproducible and its use is recommended including in DNAsamples, thus reducing the contamination with dyes such as ethidium bromide
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uso alternativo del colorante GelRed en la tincion de acidos nucleicos
Archivos de Medicina (Col), 2013Co-Authors: Paula Tatiana Uribe Echeverry, Nestor Javier Orozco Clavijo, Jhon Camilo Herrera Canon, Jhon Fredy Betancur PerezAbstract:Resumen es: Determinar la reproducibilidad en la tincion del ADN en geles de agarosa mediante el colorante GelRedTM con el fin de reemplazar el uso del bromuro de et...
David K Smith - One of the best experts on this subject based on the ideXlab platform.
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tuning gelled lyotropic liquid crystals llcs probing the influence of different low molecular weight gelators on the phase diagram of the system h2o nacl genapol la070
Soft Matter, 2019Co-Authors: Katja Steck, Jan H Van Esch, David K Smith, Cosima StubenrauchAbstract:Gelled lyotropic liquid crystals (LLCs) are highly tunable multi-component materials. By studying a selection of low molecular weight gelators (LMWGs), we find gelators that form self-assembled gels in LLCs without influencing their phase boundaries. We studied the system H2O/NaCl-Genapol LA070 in the presence of (a) the organogelators 12-hydroxyoctadecanoic acid (12-HOA) and 1,3:2,4-dibenzylidene-d-sorbitol (DBS) and (b) the hydrogelators N,N'-dibenzoyl-l-cystine (DBC) and a tris-amido-cyclohexane derivative (HG1). Visual phase studies and oscillation shear frequency sweeps confirmed that 12-HOA acts as co-surfactant (stabilizing the lamellar Lα phase and destabilizing the hexagonal H1 phase), thus preventing gelation. Conversely, DBS was a potent gelator for LLCs, with the phase boundaries un-influenced by the presence of DBS; gelled lamellar Lα, and softly-gelled hexagonal H1 phases are formed. For the hydrogelator DBC, the LLC phase boundaries were only slightly altered, but no gelled LLCs were formed. For the hydrogelator HG1, however, the phase boundaries were unaffected while gelled lamellar Lα and softly-gelled hexagonal H1 phases were formed. Temperature-dependent rheology measurements demonstrated that by changing the DBS or the HG1 concentration, the sol-gel transition temperature of the gelled lamellar Lα phase can be adjusted such that (a) Tsol-gel is below the Lα-isotropic phase transition (DBS, HG1 mass fraction η = 0.0075) and (b) Tsol-gel is above the gelled Lα-isotropic phase transition (DBS, HG1 η = 0.015). This opens the possibility of temporal materials control by addressing phase transitions in different orders. As this system contains oil and water, both the organogelator DBS and the hydrogelator HG1 can gel these LLCs, but this clearly does not apply to all organogelators/hydrogelators. The study indicates that careful optimization of LMWGs is required to avoid interaction with the surfactant layer and to optimize the Tsol-gel value, which is important for the application of LMWGs in gelled LLCs.