T. Velayutham - Academia.edu (original) (raw)
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Centre National de la Recherche Scientifique / French National Centre for Scientific Research
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Papers by T. Velayutham
Journal of oleo science, 2018
Also recognized as carbohydrate liquid crystals, glycolipids are amphiphiles whose basic unit com... more Also recognized as carbohydrate liquid crystals, glycolipids are amphiphiles whose basic unit comprises of a sugar group attached to an alkyl chain. Glycolipids are amphitropic, which means these materials form liquid crystal self-assemblies when dry (thermotropic) as well as when dissolved in solvents (lyotropic/surfactants) such as water. Many glycolipids are also naturally derived since these can be found in cell membranes. Their membrane and surfactant functions are largely understood through their lyotropic properties. While glycolipids are expected to play major roles as eco-friendly surfactants in the global surfactant market, their usefulness as thermotropic liquid crystal material is, to date, unknown, due to relatively lack of research performed and data reported in the literature. Understandably since glycolipids are hygroscopic with many hydroxy groups, removing the last trace water is very challenging. In recent time, with careful lyophilization and more consistent char...
The Journal of chemical physics, Jan 28, 2014
Glycolipid, found commonly in membranes, is also a liquid crystal material which can self-assembl... more Glycolipid, found commonly in membranes, is also a liquid crystal material which can self-assemble without the presence of a solvent. Here, the dielectric and conductivity properties of three synthetic glycolipid thin films in different thermotropic liquid crystal phases were investigated over a frequency and temperature range of (10(-2)-10(6) Hz) and (303-463 K), respectively. The observed relaxation processes distinguish between the different phases (smectic A, columnar/hexagonal, and bicontinuous cubic Q) and the glycolipid molecular structures. Large dielectric responses were observed in the columnar and bicontinuous cubic phases of the longer branched alkyl chain glycolipids. Glycolipids with the shortest branched alkyl chain experience the most restricted self-assembly dynamic process over the broad temperature range studied compared to the longer ones. A high frequency dielectric absorption (Process I) was observed in all samples. This is related to the dynamics of the hydrog...
Ferroelectrics, 2013
Synthetic pure β-anomer glycolipid with large pyroelectric coefficient (∼80 μC/m 2 K under zero a... more Synthetic pure β-anomer glycolipid with large pyroelectric coefficient (∼80 μC/m 2 K under zero applied bias field) is reported. The pyroelectric and dielectric properties of glycolipid prepared in thin films, annealed at various temperatures have been investigated. The induced polarization in the glycolipid thin films systems remains stable up to 100 • C, thus this material is appropriate for sensor materials for pyroelectric application. The real part of the dielectric constant is also low as compared to that of the other ferroelectric ceramic materials used in pyroelectric devices; therefore these new materials have significant potential application for infrared sensing devices.
Applied Clay Science, 2010
Polyurethane (PU)/organo-montmorillonite nanocomposites were prepared by in situ polymerization o... more Polyurethane (PU)/organo-montmorillonite nanocomposites were prepared by in situ polymerization of toluene diisocyanate and butanediol in the presence of different contents of organo-montmorillonite (9–18 mass%). Organo-montmorillonite were prepared by an ion exchange process of sodium montmorillonite with –NH3+ groups in polyoxyalkylene amine hydrochloride with two different molecular masses of 403 and 5000. To change the degree of surface modification, sodium montmorillonite
Journal of oleo science, 2018
Also recognized as carbohydrate liquid crystals, glycolipids are amphiphiles whose basic unit com... more Also recognized as carbohydrate liquid crystals, glycolipids are amphiphiles whose basic unit comprises of a sugar group attached to an alkyl chain. Glycolipids are amphitropic, which means these materials form liquid crystal self-assemblies when dry (thermotropic) as well as when dissolved in solvents (lyotropic/surfactants) such as water. Many glycolipids are also naturally derived since these can be found in cell membranes. Their membrane and surfactant functions are largely understood through their lyotropic properties. While glycolipids are expected to play major roles as eco-friendly surfactants in the global surfactant market, their usefulness as thermotropic liquid crystal material is, to date, unknown, due to relatively lack of research performed and data reported in the literature. Understandably since glycolipids are hygroscopic with many hydroxy groups, removing the last trace water is very challenging. In recent time, with careful lyophilization and more consistent char...
The Journal of chemical physics, Jan 28, 2014
Glycolipid, found commonly in membranes, is also a liquid crystal material which can self-assembl... more Glycolipid, found commonly in membranes, is also a liquid crystal material which can self-assemble without the presence of a solvent. Here, the dielectric and conductivity properties of three synthetic glycolipid thin films in different thermotropic liquid crystal phases were investigated over a frequency and temperature range of (10(-2)-10(6) Hz) and (303-463 K), respectively. The observed relaxation processes distinguish between the different phases (smectic A, columnar/hexagonal, and bicontinuous cubic Q) and the glycolipid molecular structures. Large dielectric responses were observed in the columnar and bicontinuous cubic phases of the longer branched alkyl chain glycolipids. Glycolipids with the shortest branched alkyl chain experience the most restricted self-assembly dynamic process over the broad temperature range studied compared to the longer ones. A high frequency dielectric absorption (Process I) was observed in all samples. This is related to the dynamics of the hydrog...
Ferroelectrics, 2013
Synthetic pure β-anomer glycolipid with large pyroelectric coefficient (∼80 μC/m 2 K under zero a... more Synthetic pure β-anomer glycolipid with large pyroelectric coefficient (∼80 μC/m 2 K under zero applied bias field) is reported. The pyroelectric and dielectric properties of glycolipid prepared in thin films, annealed at various temperatures have been investigated. The induced polarization in the glycolipid thin films systems remains stable up to 100 • C, thus this material is appropriate for sensor materials for pyroelectric application. The real part of the dielectric constant is also low as compared to that of the other ferroelectric ceramic materials used in pyroelectric devices; therefore these new materials have significant potential application for infrared sensing devices.
Applied Clay Science, 2010
Polyurethane (PU)/organo-montmorillonite nanocomposites were prepared by in situ polymerization o... more Polyurethane (PU)/organo-montmorillonite nanocomposites were prepared by in situ polymerization of toluene diisocyanate and butanediol in the presence of different contents of organo-montmorillonite (9–18 mass%). Organo-montmorillonite were prepared by an ion exchange process of sodium montmorillonite with –NH3+ groups in polyoxyalkylene amine hydrochloride with two different molecular masses of 403 and 5000. To change the degree of surface modification, sodium montmorillonite