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Nicholas L Abbott - One of the best experts on this subject based on the ideXlab platform.
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Surfactant-Induced Ordering and Wetting Transitions of Droplets of Thermotropic Liquid Crystals “Caged ” Inside Partially Filled
2016Co-Authors: Polymeric Capsules, Rebecca J Carlton, Uttam Manna, David M Lynn, Yashira M. Zayas-gonzalez, Nicholas L AbbottAbstract:ABSTRACT: We report a study of the wetting and ordering of Thermotropic Liquid Crystal (LC) droplets that are trapped (or “caged”) within micrometer-sized cationic polymeric microcapsules dispersed in aqueous solutions of surfactants. When they were initially dispersed in water, we observed caged, nearly spherical droplets of E7, a nematic LC mixture, to occupy ∼40 % of the interior volume of the polymeric capsules [diameter of 6.7 ± 0.3 μm, formed via covalent layer-by-layer assembly of branched polyethylenimine and poly(2-vinyl-4,4-dimethylazlactone)] and to contact the interior surface of the capsule wall at an angle of ∼157 ± 11°. The internal ordering of LC within the droplets corresponded to the so-called bipolar configuration (distorted by contact with the capsule walls). While the effects of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) on the internal ordering of “free ” LC droplets are similar, we observed the two surfactants to trigger strikingly different wetting and configurational transitions when LC droplets were caged within polymeric capsules. Specifically, upon addition of SDS to the aqueous phase, we observed the contact angles (θ) of caged LC on the interior surface of the capsule to decrease, resulting in a progression of complex droplet shapes, including lenses (θ ≈ 130 ± 10°), hemispheres (θ ≈ 89 ± 5°), and concave hemispheres (θ < 85°). The wetting transitions induced by SDS also resulted in changes in the internal ordering of the LC to yield states topologically equivalent to axial and radial configurations. Although topologically equivalent to free droplets, the contributions that surface anchoring, LC elasticity, and topological defects make to the free energy of caged LC droplets differ from those of free droplets. Overall, these results and others reported herein lead us to conclude that caged LC droplets offer a platform for new designs of LC-droplet-based responsive soft matter that cannot be realized in dispersions of free droplets
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surfactant induced ordering and wetting transitions of droplets of Thermotropic Liquid Crystals caged inside partially filled polymeric capsules
Langmuir, 2014Co-Authors: Rebecca J Carlton, Yashira M Zayasgonzalez, Uttam Manna, David M Lynn, Nicholas L AbbottAbstract:We report a study of the wetting and ordering of Thermotropic Liquid Crystal (LC) droplets that are trapped (or “caged”) within micrometer-sized cationic polymeric microcapsules dispersed in aqueous solutions of surfactants. When they were initially dispersed in water, we observed caged, nearly spherical droplets of E7, a nematic LC mixture, to occupy ∼40% of the interior volume of the polymeric capsules [diameter of 6.7 ± 0.3 μm, formed via covalent layer-by-layer assembly of branched polyethylenimine and poly(2-vinyl-4,4-dimethylazlactone)] and to contact the interior surface of the capsule wall at an angle of ∼157 ± 11°. The internal ordering of LC within the droplets corresponded to the so-called bipolar configuration (distorted by contact with the capsule walls). While the effects of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) on the internal ordering of “free” LC droplets are similar, we observed the two surfactants to trigger strikingly different wetting and configurati...
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influence of droplet size ph and ionic strength on endotoxin triggered ordering transitions in Liquid Crystalline droplets
Soft Matter, 2013Co-Authors: Daniel S Miller, Nicholas L AbbottAbstract:We report an investigation of ordering transitions that are induced in water-dispersed, micrometer-sized droplets of a Thermotropic Liquid Crystal (LC) by the bacterial lipopolysaccharide endotoxin. We reveal that the ordering transitions induced by endotoxin – from a bipolar state of the droplets to a radial state – are strongly dependent on the size of the LC droplets. Specifically, as the diameters of the LC droplets increase from 2 μm to above 10 μm (in phosphate buffered saline with an ionic strength of 90 mM and a pH of 7.2), we measured the percentage of droplets exhibiting a radial configuration in the presence of 100 pg mL−1 endotoxin to decrease from 98 ± 1% to 3 ± 2%. In addition, we measured a decrease in either the ionic strength or pH of the aqueous phase to reduce the percentage of droplets exhibiting a radial configuration in the presence of endotoxin. These results, when interpreted within the context of a simple thermodynamic model that incorporates the contributions of elasticity and surface anchoring to the free energies of the LC droplets, lead us to conclude that (i) the elastic constant K24 plays a central role in determining the size-dependent response of the LC droplets to endotoxin, and (ii) endotoxin-triggered ordering transitions occur only under solution conditions (pH, ionic strength) where the combined contributions of elasticity and surface anchoring to the free energies of the bipolar and radial configurations of the LC droplets are similar in magnitude. Our analysis also suggests that the presence of endotoxin perturbs the free energies of the LC droplets by ∼10−17 J per droplet, which is comparable to the standard free energy of self-association of ∼103 endotoxin molecules. The results of our investigation, when combined with prior reports of localization of endotoxin at the center of LC droplets, are consistent with the hypothesis that self-assembly of endotoxin within micrometer-sized LC droplets provides the driving force for the ordering transitions. Overall, these results advance our understanding of ordering transitions triggered by the interactions of analytes with LC droplets and, more broadly, provide guidance to the design of LC droplet systems as the basis of stimuli-responsive soft materials.
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influence of droplet size ph and ionic strength on endotoxin triggered ordering transitions in Liquid Crystalline droplets
Soft Matter, 2013Co-Authors: Daniel S Miller, Nicholas L AbbottAbstract:We report an investigation of ordering transitions that are induced in water-dispersed, micrometer-sized droplets of a Thermotropic Liquid Crystal (LC) by the bacterial lipopolysaccharide endotoxin. We reveal that the ordering transitions induced by endotoxin - from a bipolar state of the droplets to a radial state - are strongly dependent on the size of the LC droplets. Specifically, as the diameters of the LC droplets increase from 2 μm to above 10 μm (in phosphate buffered saline with an ionic strength of 90 mM and a pH of 7.2), we measured the percentage of droplets exhibiting a radial configuration in the presence of 100 pg/mL endotoxin to decrease from 98 ± 1 % to 3 ± 2 %. In addition, we measured a decrease in either the ionic strength or pH of the aqueous phase to reduce the percentage of droplets exhibiting a radial configuration in the presence of endotoxin. These results, when interpreted within the context of a simple thermodynamic model that incorporates the contributions of elasticity and surface anchoring to the free energies of the LC droplets, lead us to conclude that (i) the elastic constant K24 plays a central role in determining the size-dependent response of the LC droplets to endotoxin, and (ii) endotoxin-triggered ordering transitions occur only under solution conditions (pH, ionic strength) where the combined contributions of elasticity and surface anchoring to the free energies of the bipolar and radial configurations of the LC droplets are similar in magnitude. Our analysis also suggests that the presence of endotoxin perturbs the free energies of the LC droplets by ~10-17 J/droplet, which is comparable to the standard free energy of self-association of ~103 endotoxin molecules. These results, when combined with prior reports of localization of endotoxin at the center of LC droplets, are consistent with the hypothesis that self-assembly of endotoxin within micrometer-sized LC droplets provides the driving force for the ordering transitions. Overall, these results advance our understanding of ordering transitions triggered by the interactions of analytes with LC droplets and, more broadly, provide guidance to the design of LC droplet systems as the basis of stimuli-responsive soft materials.
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tailoring the interfaces between nematic Liquid Crystal emulsions and aqueous phases via layer by layer assembly
Nano Letters, 2006Co-Authors: Elvira Tjipto, Nicholas L Abbott, Katie D Cadwell, John F Quinn, Angus P R Johnston, Frank CarusoAbstract:We report the assembly of polyelectrolyte multilayer (PEM) films at the interfaces of Thermotropic Liquid Crystal (LC) droplets dispersed in an aqueous phase. Exposure of PEM-coated droplets to surfactant slowed the bipolar-to-radial ordering transition of the LCs by 2 orders of magnitude relative to naked droplets. This shows that PEMs can be used to influence the interactions of analytes with the LC cores of the droplets, allowing tuning of the LC emulsion sensing properties.
Daniel S Miller - One of the best experts on this subject based on the ideXlab platform.
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influence of droplet size ph and ionic strength on endotoxin triggered ordering transitions in Liquid Crystalline droplets
Soft Matter, 2013Co-Authors: Daniel S Miller, Nicholas L AbbottAbstract:We report an investigation of ordering transitions that are induced in water-dispersed, micrometer-sized droplets of a Thermotropic Liquid Crystal (LC) by the bacterial lipopolysaccharide endotoxin. We reveal that the ordering transitions induced by endotoxin – from a bipolar state of the droplets to a radial state – are strongly dependent on the size of the LC droplets. Specifically, as the diameters of the LC droplets increase from 2 μm to above 10 μm (in phosphate buffered saline with an ionic strength of 90 mM and a pH of 7.2), we measured the percentage of droplets exhibiting a radial configuration in the presence of 100 pg mL−1 endotoxin to decrease from 98 ± 1% to 3 ± 2%. In addition, we measured a decrease in either the ionic strength or pH of the aqueous phase to reduce the percentage of droplets exhibiting a radial configuration in the presence of endotoxin. These results, when interpreted within the context of a simple thermodynamic model that incorporates the contributions of elasticity and surface anchoring to the free energies of the LC droplets, lead us to conclude that (i) the elastic constant K24 plays a central role in determining the size-dependent response of the LC droplets to endotoxin, and (ii) endotoxin-triggered ordering transitions occur only under solution conditions (pH, ionic strength) where the combined contributions of elasticity and surface anchoring to the free energies of the bipolar and radial configurations of the LC droplets are similar in magnitude. Our analysis also suggests that the presence of endotoxin perturbs the free energies of the LC droplets by ∼10−17 J per droplet, which is comparable to the standard free energy of self-association of ∼103 endotoxin molecules. The results of our investigation, when combined with prior reports of localization of endotoxin at the center of LC droplets, are consistent with the hypothesis that self-assembly of endotoxin within micrometer-sized LC droplets provides the driving force for the ordering transitions. Overall, these results advance our understanding of ordering transitions triggered by the interactions of analytes with LC droplets and, more broadly, provide guidance to the design of LC droplet systems as the basis of stimuli-responsive soft materials.
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influence of droplet size ph and ionic strength on endotoxin triggered ordering transitions in Liquid Crystalline droplets
Soft Matter, 2013Co-Authors: Daniel S Miller, Nicholas L AbbottAbstract:We report an investigation of ordering transitions that are induced in water-dispersed, micrometer-sized droplets of a Thermotropic Liquid Crystal (LC) by the bacterial lipopolysaccharide endotoxin. We reveal that the ordering transitions induced by endotoxin - from a bipolar state of the droplets to a radial state - are strongly dependent on the size of the LC droplets. Specifically, as the diameters of the LC droplets increase from 2 μm to above 10 μm (in phosphate buffered saline with an ionic strength of 90 mM and a pH of 7.2), we measured the percentage of droplets exhibiting a radial configuration in the presence of 100 pg/mL endotoxin to decrease from 98 ± 1 % to 3 ± 2 %. In addition, we measured a decrease in either the ionic strength or pH of the aqueous phase to reduce the percentage of droplets exhibiting a radial configuration in the presence of endotoxin. These results, when interpreted within the context of a simple thermodynamic model that incorporates the contributions of elasticity and surface anchoring to the free energies of the LC droplets, lead us to conclude that (i) the elastic constant K24 plays a central role in determining the size-dependent response of the LC droplets to endotoxin, and (ii) endotoxin-triggered ordering transitions occur only under solution conditions (pH, ionic strength) where the combined contributions of elasticity and surface anchoring to the free energies of the bipolar and radial configurations of the LC droplets are similar in magnitude. Our analysis also suggests that the presence of endotoxin perturbs the free energies of the LC droplets by ~10-17 J/droplet, which is comparable to the standard free energy of self-association of ~103 endotoxin molecules. These results, when combined with prior reports of localization of endotoxin at the center of LC droplets, are consistent with the hypothesis that self-assembly of endotoxin within micrometer-sized LC droplets provides the driving force for the ordering transitions. Overall, these results advance our understanding of ordering transitions triggered by the interactions of analytes with LC droplets and, more broadly, provide guidance to the design of LC droplet systems as the basis of stimuli-responsive soft materials.
J T Gleeson - One of the best experts on this subject based on the ideXlab platform.
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magneto optical technique for detecting the biaxial nematic phase
Physical Review E, 2011Co-Authors: T Ostapenko, Cuiyu Zhang, Samuel Sprunt, Antal Jakli, J T GleesonAbstract:The existence of the elusive biaxial phase has been the subject of much discussion since it was predicted by Freiser in 1970. More recently, there have been numerous attempts to find a Thermotropic Liquid Crystal that exhibits a biaxial phase and with this, conflicting reports about whether such a phase has been positively identified in bent-core Liquid Crystals. One reason for the discrepancy is that there is currently no way to rule out surface effects or anchoring transitions, both of which may give a false positive identification of a uniaxial-biaxial nematic transition. We have developed a technique that uses a magnetic field to align the uniaxial director, thus widening its application to any bent-core nematic material.
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magnetic field induced isotropic to nematic Liquid Crystal phase transition
Physical Review Letters, 2008Co-Authors: T Ostapenko, Samuel Sprunt, Antal Jakli, D B Wiant, J T GleesonAbstract:We report on measurements of magnetic-field induced nematic order in the bent-core Liquid Crystal 4-chlororesorcinol bis[4-(4-$n$-dodecyloxybenzoyloxy) benzoate]. Using the 31 T solenoid at the National High Magnetic Field Laboratory, we have observed, at temperatures less than 1\ifmmode^\circ\else\textdegree\fi{} above the clearing point, a first-order transition to the nematic phase. The critical magnetic field at which this occurs increases with temperature. We discuss these results within the context of both Maier-Saupe and Landau--de Gennes mean-field models for the nematic-isotropic transition. The implications of possible tetrahedratic order are also discussed. To our knowledge, this is the first observation of such a magnetic-field induced transition in a Thermotropic Liquid Crystal; the reasons for which this behavior is now attainable are discussed.
Samuel Sprunt - One of the best experts on this subject based on the ideXlab platform.
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magneto optical technique for detecting the biaxial nematic phase
Physical Review E, 2011Co-Authors: T Ostapenko, Cuiyu Zhang, Samuel Sprunt, Antal Jakli, J T GleesonAbstract:The existence of the elusive biaxial phase has been the subject of much discussion since it was predicted by Freiser in 1970. More recently, there have been numerous attempts to find a Thermotropic Liquid Crystal that exhibits a biaxial phase and with this, conflicting reports about whether such a phase has been positively identified in bent-core Liquid Crystals. One reason for the discrepancy is that there is currently no way to rule out surface effects or anchoring transitions, both of which may give a false positive identification of a uniaxial-biaxial nematic transition. We have developed a technique that uses a magnetic field to align the uniaxial director, thus widening its application to any bent-core nematic material.
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magnetic field induced isotropic to nematic Liquid Crystal phase transition
Physical Review Letters, 2008Co-Authors: T Ostapenko, Samuel Sprunt, Antal Jakli, D B Wiant, J T GleesonAbstract:We report on measurements of magnetic-field induced nematic order in the bent-core Liquid Crystal 4-chlororesorcinol bis[4-(4-$n$-dodecyloxybenzoyloxy) benzoate]. Using the 31 T solenoid at the National High Magnetic Field Laboratory, we have observed, at temperatures less than 1\ifmmode^\circ\else\textdegree\fi{} above the clearing point, a first-order transition to the nematic phase. The critical magnetic field at which this occurs increases with temperature. We discuss these results within the context of both Maier-Saupe and Landau--de Gennes mean-field models for the nematic-isotropic transition. The implications of possible tetrahedratic order are also discussed. To our knowledge, this is the first observation of such a magnetic-field induced transition in a Thermotropic Liquid Crystal; the reasons for which this behavior is now attainable are discussed.
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dynamic light scattering study of biaxial ordering in a Thermotropic Liquid Crystal
Physical Review Letters, 2006Co-Authors: Krishna Neupane, Shinwoong Kang, Sunil K Sharma, Daniel Carney, T Meyer, Georg H Mehl, David W Allender, Satyendra Kumar, Samuel SpruntAbstract:Dynamic light scattering from orientational order fluctuations in a Liquid Crystalline tetrapode reveals successive, weakly first-order isotropic to uniaxial and uniaxial to biaxial nematic phase transitions. The order parameter relaxation rates exhibit temperature dependences consistent with Landau-de Gennes mean field theory. Combined with previous evidence of a second-order uniaxial-biaxial transition in a closely related tetrapode, the present study supports the existence of a nematic-nematic tricritical point in Thermotropic Liquid Crystals.
Sol Lopezandres - One of the best experts on this subject based on the ideXlab platform.
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study of the polymorphism in copper ii decanoate through its phase diagram with decanoic acid and texture of the columnar Thermotropic Liquid Crystal developable domains in this and similar systems
Crystal Growth & Design, 2015Co-Authors: Ramos M. Riesco, Francisco Javier Martinezcasado, J Rodriguez A Cheda, M Redondo I Yelamos, Alejandro Fernandezmartinez, Sol LopezandresAbstract:A new third polymorph of copper(II) decanoate has been found by two methods: from the Crystallization of the salt–acid solution and from a specific thermal treatment of the polymorph obtained in n-heptane. The new polymorph, whose Crystal structure has been solved for the first time, is the most stable from the thermodynamic point of view. It presents a bilayer structure, but with two different types of paddle-wheels catenae with opposite orientations. This polymorphism as well as the temperature vs composition phase diagram of the system, [(1 – x) C9H21CO2H + (x) (C9H21CO2)2Cu], were solved by differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, pair distribution function, and optical microscopy. The singularities of the phase diagram are (a) a Krafft-like process of molecular association of the copper(II) decanoate into the acid solution, at about T = 361.5 K and x = 0.022 (forming salt-acid adducts of 1:1 stoichiometry); (b) a fusion transition as an invariant ...
