References of "Razafindralambo, Hary"
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See detailFundamental property and functional aptitude relationships in emulsion and foam applications of amphiphilic compounds
Razafindralambo, Hary ULg

Conference (2013, April 11)

Amphiphilic compounds are issued of a combination of two opposite entities, covalently assemblied within a single structure. By the diversity of the origin, class, number of monomer and substitute, size ... [more ▼]

Amphiphilic compounds are issued of a combination of two opposite entities, covalently assemblied within a single structure. By the diversity of the origin, class, number of monomer and substitute, size, linker or spacer, stereochemistry of the molecular entities, their chemical structure may be very different but also close each other. However, they may fulfill the same role in reducing surface and interfacial free energy in dynamic or static ways, ensuring especially the formation of dispersed systems like emulsion and foam. If the relationships between the structural variable and fundamental properties are strictly chemical residue dependent, those between fundamental and functional aptitudes are not necessarily. In this case, general and universal rules may exist, whatever the kind of amphiphilic compounds. In order to achieve a rational design for any expected functionality, we attempt to find out some predictive and conception rules from a lot of screening data of fundamental and functional properties. In this communication, some correlations between fundamental data related to surface and interfacial properties, measured by molecule adsorption or spreading under dynamic or static mode, in compression or dilation of adsorbed or spread film, and emulsifying and foaming performances of various bio-based surfactants will be presented. [less ▲]

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See detailPhoton correlation spectroscopy for molecular self-assembly investigations
Razafindralambo, Hary ULg

Conference (2013, April 11)

The molecular self-assembly performance is among the most important functionalities of amphiphilic compounds in colloidal system areas. This aptitude is required in numerous applications, depending on ... [more ▼]

The molecular self-assembly performance is among the most important functionalities of amphiphilic compounds in colloidal system areas. This aptitude is required in numerous applications, depending on solubilization, hydrotropy, rheology, separation, loading and delivery, encountered in biological and industrial processes. The main physicochemical parameter predicting the capacity of amphiphiles to self-assembly in bulk liquid, aqueous (normal micelles) or non-aqueous phase (reverse micelles), is the pair critical micelle concentration (CMC) and temperature (CMT). A variety of methods based on surface tension, spectral changes, and electrical conductivity are commonly used for determining the value of CMC. The choice usually depends on the ionic or non-ionic nature of the amphiphilic compounds. In this communication, a standard Photon Correlation Spectroscopy (PCS), also known Light Scattering-based technique for CMC determination will be theoretically and practically described in details. Its particular interest for measuring the performance of non-ionic and very high hydrophobic tail, mono or disubstituted carbohydrate-based compounds, from C16 alkyl chain, will be demonstrated. Such a method is advantageous regarding the time, amount, and resolution required, but also for additional information on micelle size, aggregate number, and stability it may provide, compared to surface tension and electrical conductivity-based measurements. [less ▲]

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See detailAmphiphilic structure-surface property relationships of monosaccharide-based surfactants
Razafindralambo, Hary ULg; Nicks, Francois ULg; Richard, Gaetan ULg et al

Poster (2013, April 08)

A set of monosaccharide-based renewable surfactants has been prepared, structurally checked, and systematically screened for different activities and functionalities. These compounds vary in the polar ... [more ▼]

A set of monosaccharide-based renewable surfactants has been prepared, structurally checked, and systematically screened for different activities and functionalities. These compounds vary in the polar head group, linker, and hydrophobic tail. Beyond the goal to find out the most potential valuable surfactants for each measurement, relationships between chemical structure, basic properties, and functionalities have been examined by comparing compounds differing in a single structural variable. In this paper, we show and explain the impact of the anomeric alpha or bêta, neutral or acid sugar derivatives, equatorial or axial position of hydroxyl group, alkyl chain substitute attachment position, number, and length on surface properties of sugar-based surfactants. [less ▲]

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See detail(Bio)-amphiphilic compounds as biohybrid materials: the case of peptidolipids and glycolipids
Razafindralambo, Hary ULg

Conference (2013, March)

(Bio)-hybrid compounds are constituted by at least two distinct classes of component covalently linked within the same structure. Amphiphilic compounds of peptide- and oligosaccharide-lipid groups are ... [more ▼]

(Bio)-hybrid compounds are constituted by at least two distinct classes of component covalently linked within the same structure. Amphiphilic compounds of peptide- and oligosaccharide-lipid groups are among representatives bio-hybrid molecules with increasing interests since each of them contains two entities belonging to important categories of biological molecules like proteins, carbohydrates, and lipids. The strength of such compounds is by far their possibility to exhibit multifunctional properties and activities, specifically developed by each of these three biomolecule classes. In addition, their intermediate size with regard to small and large molecular structures may present certain undeniably advantages, for instance, a lower diffusivity and a greater solubility in aqueous solution compared to small and polymeric surfactants, respectively. In this paper, the case of peptide and carbohydrate-based surfactants containing a linear series of alkyl fats will be presented and discussed regarding to interfacial properties, colloidal stabilities, and biological activities with the perspective of getting more efficient hybrid compounds by rational design approaches. [less ▲]

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See detailInvestigation of Structure-Fundamental/Functional Property Relationships of (Bio)-surfactants for a Rational Design of their Preparation and Use in Food and Non-food applications
Razafindralambo, Hary ULg

Conference (2012, May 01)

(Bio)-surfactants are among the most versatile compounds in our planet, either in nature or in biological systems, as well as in manufactured products. Increasing knowledge on the relationships between ... [more ▼]

(Bio)-surfactants are among the most versatile compounds in our planet, either in nature or in biological systems, as well as in manufactured products. Increasing knowledge on the relationships between their structure, fundamental properties, and functionalities in simple, and thereafter in more complicated models, are therefore the key factor on their rational preparation and use for any applications. In the present communication, the effect of different structural entities of (bio)surfactants, especially Carbohydrate-based amphiphilic compounds, including monomeric, oligomeric, and polymeric surfactants, on their interfacial properties at short time (under dynamic conditions) and long time (at the equibrium), and the impact of such fundamental properties through physico-chemical parameters on the formation and stability of colloidal systems (micelles, foams, emulsions) will be presented. Some perspectives in their applications will be discussed. [less ▲]

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See detailAdsorption kinetics of total proteose peptone fractions at the air-water and n-dodecane-water interface
Karamoko, Gaoussou ULg; Razafindralambo, Hary ULg; Danthine, Sabine ULg et al

Poster (2012, March 26)

Surface properties of whey proteins are essential in applications requiring oil emulsification in an aqueous phase, or foam structure formation [1]. The adsorption at interfaces constitutes then an ... [more ▼]

Surface properties of whey proteins are essential in applications requiring oil emulsification in an aqueous phase, or foam structure formation [1]. The adsorption at interfaces constitutes then an approach of the physico-chemical mechanisms of foaming and emulsifying properties. Proteose-peptone is the minor fraction of whey's protein, thermoresistant and acid-soluble protein fraction extracted from milk [2], and known for its interesting surface properties [3]. In this study, the TPP fractions were extracted from skimmed milk UHT (milk TPP) and whey protein concentrate (WPC TPP). Their adsorption kinetics at the air-water and n-dodecane-water interfaces was investigated by the drop volume tensiometer method. Protein solutions of 1% (w/v) were <br />characterized under dynamic condition at various pH (4.0; native pH 4.67- 4.70 and 7.0). Milk TPP showed the lowest values as well as a faster reduction in surface tension at both considered interfaces. Therefore, TPP were found to e effective as surfactants. These results let us to presage good emulsifying and foaming properties of milk TPP compared to WPC TPP. The considerable influence of pH and extraction source on proteose-peptone's interfacial property have been highlighted. [less ▲]

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See detailImpact of the alkyl chain carbon atom number of uronic acid-derivative surfactants on interfacial and colloidal systems
Razafindralambo, Hary ULg; Richard, Gaetan ULg; Laurent, Pascal ULg et al

Poster (2012, March 26)

Uronic acid-derivative surfactants represent today an attractive group of Carbohydrate-based amphiphilic compounds for both fundamental and practical reasons [1,2]. In the continuity of our screening of ... [more ▼]

Uronic acid-derivative surfactants represent today an attractive group of Carbohydrate-based amphiphilic compounds for both fundamental and practical reasons [1,2]. In the continuity of our screening of their basic properties, and the approach in establishing relationships between their structure and properties [3,4], the impact of the alkyl chain carbon atom number on interfacial and colloidal systems has been systematically investigated. In this communication, the effect of odd-even number of carbon atom from C11 to C18, and the particular behavior of long chain derivatives on interfacial properties, as well as their impact on the formation and stability of colloidal systems, are presented. Experimental approaches have been conducted by investigating their properties and behaviors at gas-liquid and liquid-liquid under dynamic, equilibrium, and oscillatory interfacial conditions. Results are completed by and discussed with single molecule models established by theoretical approaches. [1] Razafindralambo, H.;Blecker, C.; Paquot, M., Screening of Basic Properties of Amphiphilic Molecular Structures for Colloidal System Formation and Stability. In Amphiphiles: Molecular Assembly and Applications, American Chemical Society: 2011; Vol. 1070, pp 53-66. [2] Laurent, P.; Razafindralambo, H.; Wathelet, B.; Blecker, C.; Wathelet, J.; Paquot, M., Synthesis and Surface-Active Properties of Uronic Amide Derivatives, Surfactants from Renewable Organic Raw Materials. J. Surfactants Deterg. 2011, 14, 51-63. [3] Razafindralambo, H.; Richel, A.; Wathelet, B.; Blecker, C.; Wathelet, J.; Brasseur, R.; Lins, L.; Miñones, J.; Paquot, M., Monolayer properties of uronic acid bicatenary derivatives at the air-water interface: effect of hydroxyl group stereochemistry evidenced by experimental and computational approaches. Physical chemistry chemical physics: PCCP 2011, 13 15291-15298. [4] Razafindralambo, H.; Blecker, C.; Mezdour, S.; Deroanne, C.; Crowet, J.; Brasseur,R.; Lins, L.; Paquot, M., Impacts of the Carbonyl Group Location of Ester Bond on Interfacial Properties of Sugar-Based Surfactants: Experimental and Computational Evidences. The journal of physical chemistry. B 2009, 113, 8872-8877. [less ▲]

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See detailRelationships between structure-interfacial-functional properties: The rheology at interfaces from small to polymeric carbohydrate-based surfactants
Razafindralambo, Hary ULg

Conference (2012, March 25)

Amphiphilc molecules are one of the most important compounds in our planet owing to their fundamental role as catalysts of interfacial free energy in nature, biological systems, and manufacturated ... [more ▼]

Amphiphilc molecules are one of the most important compounds in our planet owing to their fundamental role as catalysts of interfacial free energy in nature, biological systems, and manufacturated products [1]. Their chemical structure and configuration, which governs their properties and activities, may be classified in small, intermediate, and large sizes. To better understand the effect of such a parameter, the behaviors of various carbohydrate-based surfactants, from small to polymeric molecular structures at the air-water interface, and in bulk liquid for their ability to form and stabilize related colloidal systems like micelles and foams have been investigated. In particular, rheological properties including elasticity and viscosity components at the air-water interface have been determined by oscillatiory mode under different oscillation frequency and surfactant concentration conditions using a pending drop tensiometer system. Their micellar and foaming properties have been characterized and evaluated in terms of CMC-micelle size and formation-stability, respectively. Reference: [1] Razafindralambo, H.; Blecker, C.; Paquot, M., Screening of Basic Properties of Amphiphilic Molecular Structures for Colloidal System Formation and Stability. In Amphiphiles: Molecular Assembly and Applications, Ed. R. Nagarajan, American Chemical Society: 2011;. Vol. 1070, pp 53-66. [less ▲]

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See detailCarbohydrate-based surfactants: structure-activity relationships
Razafindralambo, Hary ULg; Blecker, Christophe ULg; Paquot, Michel ULg

in Nawaz, Zeeshan; Naveed, Shahid (Eds.) Advances in Chemical Engineering (2012)

The aim of the present contribution is: (1) to review CBS in terms of structural classification based on their molecular size (mono-, oligo-, polymeric surfactants), geometry (standard, bipolar or ... [more ▼]

The aim of the present contribution is: (1) to review CBS in terms of structural classification based on their molecular size (mono-, oligo-, polymeric surfactants), geometry (standard, bipolar or bolaform, and gemini surfactants), and the nature of the polar headgroup (charged or not, cyclic or not), the apolar tail (number and length of alkyl chain), and the linker (amide, ester, ...) and/or the spacer; (2) to present systematically results on structure- activity relationships of uronic acid derivatives (UADs), a particular class of carbohydrate-based surfactants. These concern the impact of each structural entity including the polar headgroup (stereochemistry), apolar tail (chain length, number, and unsaturation), and linkage/spacer, on the performance of UADs to change surface properties, and possibly, to form and stabilize colloidal systems. [less ▲]

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See detailLiquid Crystalline Phases Induced by the Hydroxyl Group Stereochemistry of Amphiphilic Carbohydrate Bicatenary Derivatives
Razafindralambo, Hary ULg; Richel, Aurore ULg; Paquot, Michel ULg et al

in Journal of Physical Chemistry B (2012), 116(13), 3998-4005

Liquid-crystals (LC) may exist in different phases depending upon the orientational and positional orders of molecules in the material. Here, we demonstrate that the class of LC state induced by ... [more ▼]

Liquid-crystals (LC) may exist in different phases depending upon the orientational and positional orders of molecules in the material. Here, we demonstrate that the class of LC state induced by amphiphilic carbohydrate bicatenary derivatives is strictly a hydroxyl group stereochemistry-dependent. This statement results from the experimental and theoretical investigations of surface film (2D) and bulk solid (3D) thermal behavior of synthetic stereoisomers n-tetradecyl (-D-n-tetradecyl) galacto- and gluco-pyranosiduronate, with an axial (GalA-C14/14) or equatorial (GlcA-C14/14) hydroxyl group at the fourth carbon, respectively. Surface pressure-area isotherms (283 K to 310 K), differential scanning calorimetry thermograms (223 K to 573 K), and polarized optical textures (298-363 K) reveal that GlcA-C14/14 organizes as a smectic LC-like phase (positional or lateral order) whereas the analogous stereoisomeric GalA-C14/14 behaves as a nematic LC-like phase (orientational order). Thermodynamic investigations and molecular dynamics models computed under similar temperature conditions provide consistent data with physical properties resulting from experimental approaches. [less ▲]

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See detailBINDING INTERACTIONS OF URONIC ACID DERIVATIVES TO LIPID VESICLES INVESTIGATED BY ISOTHERMAL TITRATION CALORIMETRY
Razafindralambo, Hary ULg; Laurent, Pascal ULg; Wathelet, Jean-Paul ULg et al

Poster (2011, November 12)

Uronic acid derivatives (UAD) constitute a particular class of carbohydrate-based small compounds, which are receiving growing interests today for many reasons. Beyond their excellent environmental ... [more ▼]

Uronic acid derivatives (UAD) constitute a particular class of carbohydrate-based small compounds, which are receiving growing interests today for many reasons. Beyond their excellent environmental compatibility, their potentiality mainly arises from the large abundance of their precursors from renewable resources, and the quasi-unlimited availability of their molecular structure and geometry [1]. Such a structural diversity allows them to be a typical compound class for the structure-activity relationship investigation using simplest models. This approach is very important for predicting their functionalities and activities. Among others, searching specific and potent biological activities against target molecules, cells, and micro-organisms is a big challenge today. In this context, binding interactions of three UAD having different hydrophobic residues (allyl, benzyl, and cyclohexyl) to 1-palmitoyl-2-oleyl-sn-glycerol-3-phosphatidylcholine (POPC) vesicles have been investigated using Isothermal Titration Calorimetry (ITC) technique [2]. The binding affinity (Ka) to the membrane model at 25°C has been determined and compared for the three compounds. Based on thermograms resulting from UAD aqueous solution titration experiments, with and without POPC vesicles, it clearly appears that both derivatives with a cyclic residue interact stronger with the lipid membrane model than their linear derivative counter-part, which exhibits almost no interaction. Moreover, the derivative compound with a cyclohexyl residue saturates faster POPC vesicles than that with a benzyl residue. We conclude that: (a) UAD having a cyclic hydrophobic residue, either saturated or unsaturated, bind more easily to the lipid membrane model than a linear one ending with a double bond; (b) the greater the number of hydrogen in the UAD residue chemical structure (saturated bonds), the stronger their binding affinity to POPC vesicles, suggesting the importance of H-bonding to such a lipid membrane model. The Ka mean value of the best tested UAD, i.e. with a cyclohexyl residue, is about 5.103 M-1. [1] Razafindralambo, H.; Blecker, C; and M. Paquot., Screening of basic properties of amphiphilic molecular the structures for colloidal system formation and stability: the case of carbohydrate-based surfactants in: Amphiphiles: Molecular Assembly and Applilcations, ed. R. Nagarajan, ACS, Washignton, 2011, (In press). [2] Razafindralambo, H.; Dufour, S.; Paquot, M.; Deleu, M., Thermodynamic studies of the binding interactions of surfactin analogues to lipid vesicles: application of isothermal titration calorimetry. J. Therm. Anal. Calorim., 2009, 9 (3), 817-821. Acknowledgment: This work was supported by Belgian Walloon Region with DG06 research project of excellence (TECHNOSE). [less ▲]

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See detailScreening of Basic Properties of Amphiphilic Molecular Structures for Colloidal System Formation and Stability. The Case of Carbohydrate-Based Surfactants
Razafindralambo, Hary ULg; Blecker, Christophe ULg; Paquot, Michel ULg

in In Amphiphiles: Molecular Assembly and Applications; Nagarajan, R. (2011)

Colloidal systems are bubbles, droplets, or/and particles dispersed in a continuous media, which are encountered in nature, biological system, and manufactured products. As site of interfaces between at ... [more ▼]

Colloidal systems are bubbles, droplets, or/and particles dispersed in a continuous media, which are encountered in nature, biological system, and manufactured products. As site of interfaces between at least two bulk phases, their formation and stability need the presence of amphiphilic molecules. Carbohydrate-based surfactants (CBS) take part of these groups of compound having numerous attractive features: an abundance of precursor raw material sources, an excellent environmental compatibility, and a possible quasi-unlimited design of their molecular structure and geometry by different preparation routes. Numerous properties and activities including the aptitude to form and stabilize colloidal systems are therefore expected from a wide range of CBS compounds. Screening of their interfacial behaviors, which govern their functionalities in colloidal system properties, are then relevant in fundamental and practical point of view. In this chapter, interfacial properties of uronic acid-based surfactants are presented as examples of screening approaches. Experimental measurements of both dynamic and equilibrium properties at air-liquid and liquid-liquid interfaces, as well as a computational approach are reported. [less ▲]

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See detailScreening of Basic Properties of Amphiphilic Molecular Structures for Colloidal System Formation and Stability: The Case of Carbohydrate-Based Surfactants
Razafindralambo, Hary ULg; Blecker, Christophe ULg; Paquot, Michel ULg

in Nagarajan, Ramananthan (Ed.) Amphiphiles: Molecular Assembly and Applications (2011, September 19)

Colloidal systems are bubbles, droplets, or/and particles dispersed in a continuous media, which are encountered in nature, biological system, and manufactured products. As site of interfaces between at ... [more ▼]

Colloidal systems are bubbles, droplets, or/and particles dispersed in a continuous media, which are encountered in nature, biological system, and manufactured products. As site of interfaces between at least two bulk phases, their formation and stability need the presence of amphiphilic molecules. Carbohydrate-based surfactants (CBS) take part of these groups of compound having numerous attractive features: an abundance of precursor raw material sources, an excellent environmental compatibility, and a possible quasi-unlimited design of their molecular structure and geometry by different preparation routes. Numerous properties and activities including the aptitude to form and stabilize colloidal systems are therefore expected from a wide range of CBS compounds. Screening of their interfacial behaviors, which govern their functionalities in colloidal system properties, are then relevant in fundamental and practical point of view. In this chapter, interfacial properties of uronic acid-based surfactants are presented as examples of screening approaches. Experimental measurements of both dynamic and equilibrium properties at air-liquid and liquid-liquid interfaces, as well as a computational approach are reported. [less ▲]

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See detailMonolayer Properties of Uronic Acid Bicatenary Derivatives at the Air-Water Interface: Effect of Hydroxyl Group Stereochemistry Evidenced by Experimental and Computational Approaches
Razafindralambo, Hary ULg; Richel, Aurore ULg; Wathelet, Bernard ULg et al

in Physical Chemistry Chemical Physics [=PCCP] (2011), 13(33), 1529115298

By screening uronic acid-based surfactant interfacial properties, the effect of the hydroxyl group stereochemistry (OH-4) on the conformation of bicatenary (disubstituted) derivatives at the air–water ... [more ▼]

By screening uronic acid-based surfactant interfacial properties, the effect of the hydroxyl group stereochemistry (OH-4) on the conformation of bicatenary (disubstituted) derivatives at the air–water interface has been evidenced by experimental and computational approaches. Physical and optical properties of a monolayer characterized by Langmuirfilmbalance, Brewster angle microscopy, and ellipsometry at 20°C reveal that the derivative of glucuronate (C14/14–GlcA) forms a more expanded monolayer, and shows a transition state under compression, in the opposite to that of galacturonate (C14/14–GalA). Both films are very mechanically resistant (compression modulus > 300m Nm-1) and stable (collapse pressure exceeding 60mNm-1), while that of C14/14–GalA exhibits a very high compression modulus up to 600mNm-1 like films in the solid state. Computational approaches provide single and assembly molecular models that corroborate the molecule expansion degree and interactions data from experimental results. Differences in the molecular conformation and film behaviours of uronic acid bicatenary derivatives at the air–water interface are attributed to the intra-H-bonding formation, which is more favourable with an OH-4 in the axial (C14/14–GalA) than in the equatorial position (C14/14–GlcA). [less ▲]

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See detailAn Overview Of Methodology For Predicting Activities And Functionalities Of A Wide Range Of Carbohydrate- Based Surfactants From Their Fundamental Properties
Razafindralambo, Hary ULg; Blecker, Christophe ULg; Paquot, Michel ULg

in 8th World surfactant congress and business convention (2011, June 06)

Introduction and Background: Carbohydrate-based surfactants (CBS) are, today, among the most attractive amphiphilic compounds owing to their high potentiality for a large product concept. The main ... [more ▼]

Introduction and Background: Carbohydrate-based surfactants (CBS) are, today, among the most attractive amphiphilic compounds owing to their high potentiality for a large product concept. The main fundamental reasons are the abundance of their precursors from renewable resources, the excellent environmental compatibility, and the quasi-unlimited availability of their molecular structure and geometry. Based on the latter aspect, CBS would be expected to generate a wide range of functionalities and activities for food and non-food applications. All kinds of amphiphilic compounds including small surfactants, bolaforms, geminis, oligomeric, and polymeric molecules with a single or a multiple hydrophobic tails can be designed by synthetic routes thanks to a large number of reactive chemical groups in their basic structure. Consequently, various methodologies are required, and could be used in complementary for identifying all of their potentiality for further development. Methodology: The methodology is based on the characterization in the laboratory scale, i.e. using only small amounts of sample, of CBS properties at fluid and solid interfaces, in bulk liquid phases, and at the solid state with simplified models. Results and Discussion: In this communication, an overview of functionality and activity-predicting methods for a wide range of CBS structures varying in head polar groups, hydrophobic tail and number, and linkers will be presented and discussed. Performances and complementarities of different approaches, methodologies, and techniques will be emphasized. These include sample preparation and analysis procedures, interfacial-characterizing instruments, mainly tensiometers and Langmuir balances used both in dynamic and (quasi)-static modes, particle size and electrical charge analyser, and (micro)calorimeters using differential scanning, isothermal titration, and thermogravimetry methods. Conclusion: The knowledge of these basic properties is helpful for predicting their main activities and functionalities like their aptitude for forming and stabilizing colloidal systems, and for developing biological activities. This is also necessary for the rational design of CBS amphiphilic structure regarding to specific properties. The same approach can also be applied for other required features as the compound stability, toxicity, and biodegradability. [less ▲]

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See detailStructure-Surface Activity Relationships Of Uronic Acid-Derivative Surfactants From Renewable Resources Applications
Razafindralambo, Hary ULg; Richel, Aurore ULg; Richard, Gaetan ULg et al

Poster (2011, June)

Introduction and Background: Uronic acid-derivative surfactants are amphiphilic compounds with growing interests owing to their potential applications in various areas [1]. This class of carbohydrate ... [more ▼]

Introduction and Background: Uronic acid-derivative surfactants are amphiphilic compounds with growing interests owing to their potential applications in various areas [1]. This class of carbohydrate-based surfactants can be easily prepared from renewable raw materials in a wide range of structure by modular synthesis thanks to the presence of one carboxylic and numerous hydroxyl groups. The polar head group configurations according to the stereochemistry of OH groups, and geometry (cyclic or not), the hydrophobic tail (number and length of alkyl chain), and the type of linker (ester, acetal and amide, etc) are among the main variables in their structural entities. Therefore, the investigation of their structure-surface activity relationships appears valuable for increasing backgrounds, and achieving a rational design for selecting the best structures to be used in different industrial fields [2]. Methodology: A few analogous of glucuronic acid-derivative surfactants have been synthesized by chemical or enzymatic routes. After purification, their structure has been confirmed by various spectroscopic techniques (RMN, MS, IR). Surface tensions of true aqueous solution have been then measured in dynamic and static modes using a series of complementary techniques. Critical micelle concentrations, minimum molecular areas, and maximum surface excesses have also been determined. Results and Discussion: Glucuronic acid derivative surfactants under investigation vary in the polar head group configuration including cyclic or non-cyclic structure and α or β anomeric form, in the hydrophobic tail regarding to the chain length (C8 to C14), the presence of a double bond, as well as an OH group at the terminal carbon, and in the type of linker, ester in C6 or acetal in C1. Results showed that all of these structural attributes affect both dynamic and equilibrium surface properties of glucuronic acid -based surfactants. Conclusion: A set of synthetic glucuronic acid-based surfactants varying in the polar head group, hydrophobic tail, and linker allow us to generate various surface-active properties at the air-water interface, and to increase the knowledge on relationships between their structure and surface-active properties. [1] Laurent, P.; Razafindralambo, H.; Wathelet, B.; Blecker, C.; Wathelet, J.-P.; Paquot, M., Synthesis and Surface-Active Properties of Uronic Amide Derivatives, Surfactants from Renewable Organic Raw Materials. Journal of Surfactants and Detergents 2010, in press. [2] Razafindralambo, H.; Blecker, C.; Mezdour, S.; Deroanne, C.; Crowet, J.; Brasseur, R.; Lins, L.; Paquot, M., Impacts of the Carbonyl Group Location of Ester Bond on Interfacial Properties of Sugar-Based Surfactants: Experimental and Computational Evidences. The Journal of Physical Chemistry B 2009, 113 (26), 8872-8877. Acknowledgment: This work was supported by Belgian Walloon Region within DGTRE research project of excellence (TECHNOSE). [less ▲]

Detailed reference viewed: 115 (26 ULg)
See detailAn Overview Of Methodology For Predicting Activities And Functionalities Of A Wide Range Of Carbohydrate- Based Surfactants From Their Fundamental Properties
Razafindralambo, Hary ULg

Conference (2011, June)

Introduction and Background: Carbohydrate-based surfactants (CBS) are, today, among the most attractive amphiphilic compounds owing to their high potentiality for a large product concept. The main ... [more ▼]

Introduction and Background: Carbohydrate-based surfactants (CBS) are, today, among the most attractive amphiphilic compounds owing to their high potentiality for a large product concept. The main fundamental reasons are the abundance of their precursors from renewable resources, the excellent environmental compatibility, and the quasi-unlimited availability of their molecular structure and geometry. Based on the latter aspect, CBS would be expected to generate a wide range of functionalities and activities for food and non-food applications. All kinds of amphiphilic compounds including small surfactants, bolaforms, geminis, oligomeric, and polymeric molecules with a single or a multiple hydrophobic tails can be designed by synthetic routes thanks to a large number of reactive chemical groups in their basic structure. Consequently, various methodologies are required, and could be used in complementary for identifying all of their potentiality for further development. Methodology: The methodology is based on the characterization in the laboratory scale, i.e. using only small amounts of sample, of CBS properties at fluid and solid interfaces, in bulk liquid phases, and at the solid state with simplified models. Results and Discussion: In this communication, an overview of functionality and activity-predicting methods for a wide range of CBS structures varying in head polar groups, hydrophobic tail and number, and linkers will be presented and discussed. Performances and complementarities of different approaches, methodologies, and techniques will be emphasized. These include sample preparation and analysis procedures, interfacial-characterizing instruments, mainly tensiometers and Langmuir balances used both in dynamic and (quasi)-static modes, particle size and electrical charge analyser, and (micro)calorimeters using differential scanning, isothermal titration, and thermogravimetry methods. Conclusion: The knowledge of these basic properties is helpful for predicting their main activities and functionalities like their aptitude for forming and stabilizing colloidal systems, and for developing biological activities. This is also necessary for the rational design of CBS amphiphilic structure regarding to specific properties. The same approach can also be applied for other required features as the compound stability, toxicity, and biodegradability. [less ▲]

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See detailEffect of ageing on different egg yolk fractions on surface properties at the air–water interface
Freschi, Jérôme ULg; Razafindralambo, Hary ULg; Danthine, Sabine ULg et al

in International Journal of Food Science & Technology (2011), 46

The aim of this study was to evaluate the impact of egg ageing on the surface properties of whole and fractionated yolk at the air–water interface. Eggs were stored at 4 Cfor 24 h, 1 week and 3 weeks ... [more ▼]

The aim of this study was to evaluate the impact of egg ageing on the surface properties of whole and fractionated yolk at the air–water interface. Eggs were stored at 4 Cfor 24 h, 1 week and 3 weeks after laying.A laboratory scale fractionation process was then applied at each ageing time. Egg yolk was separated into two fractions, plasma composed of low-density lipoproteins (LDLs) and livetins, and granules formed by highdensity lipoproteins (HDLs), phosvitins and LDLg (g = granule). Moreover, recombined plasma and granules fractions were investigated to highlight a potential synergic effect on surface properties. Results have shown the main contribution of LDLs on surface properties of yolk and an improvement of granules surface properties when they are disrupted. Moreover, ageing affected surface properties differently depending on the considered fractions. Broken LDLsand disrupted granules could explain this observed behaviour. Recombined fractions showed different compression isotherms at the air–water interface than whole yolk. [less ▲]

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See detailEtude des interactions membranaires de dérivés de l’acide glucuronique par calorimétrie à titrage isotherme
Laurent, Pascal ULg; Razafindralambo, Hary ULg; Paquot, Michel ULg

Poster (2011)

Dans le cadre de la valorisation de la biomasse et des glucides provenant de l’hydrolyse de matières premières renouvelables, différents dérivés d’acides uroniques ont été synthétisés en vue d’évaluer ... [more ▼]

Dans le cadre de la valorisation de la biomasse et des glucides provenant de l’hydrolyse de matières premières renouvelables, différents dérivés d’acides uroniques ont été synthétisés en vue d’évaluer leurs propriétés en tant qu’agents tensioactifs biocompatibles et biodégradables. Une nouvelle stratégie de synthèse assistée par micro-ondes, efficace et respectueuse de l'environnement, a par ailleurs permis de synthétiser quantitativement différentes D-glucofuranosidurono-6,3-lactones monosubstituées hydrosolubles au départ d'acide D-glucuronique non protégé en utilisant un catalyseur acide supporté. Ces lactones appartiennent à la famille des glycosurfactants non-ioniques dont les applications couvrent un vaste domaine, aussi bien dans l’industrie pharmaceutique, cosmétique ou alimentaire. Une première approche en vue d’évaluer leurs activités biologiques consiste en l’étude des paramètres d’interactions moléculaires de ces lactones vis-à-vis d’une membrane biologique modèle (1-palmitoyl-2-oleyl-sn-glycerol-3-phosphatidylcholine) par calorimétrie à titrage isotherme (Isothermal Titration Calorimetry – ITC). [less ▲]

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See detailSynthesis and Surface-Active Properties of Uronic Amide Derivatives, Surfactants from Renewable Organic Raw Materials
Laurent, Pascal ULg; Razafindralambo, Hary ULg; Wathelet, Bernard ULg et al

in Journal of Surfactants and Detergents (2011), 14(1), 51-63

Short chemical syntheses were developed to produce a new set of surfactants from uronic acids derived from widely available raw material. Three different strategies were used to synthesise uronic amide ... [more ▼]

Short chemical syntheses were developed to produce a new set of surfactants from uronic acids derived from widely available raw material. Three different strategies were used to synthesise uronic amide derivatives, the structures of which were totally characterized by spectrometric methods (IR, MS, 1H-RMN and 13C-RMN). The best one, using an acid chloride as synthetic intermediate, furnished the expected amides as a mixture of anomers in 46 to 58 % global yield. Surface-active properties (CMC, g cmc, Tmax, Amin) of homologous series of uronic acid N-alkylamides from C8 to C18 were also assessed. In general, these sugar-based surfactants exhibited good surface-activities, and appeared as valuable non ionic surfactants compared to Triton X-100, the most well-known non ionic surfactant. Increasing the alkyl chain length influenced the CMC values for both glucuronic and galacturonic N-alkylamide derivatives. The galacturonic N-alkylamides decreased g cmc at slower values than their counterpart's glucuronic N-alkylamides. [less ▲]

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