Article

Polysaccharide/Surfactant complexes at the air-water interface – Effect of the charge density on interfacial and foaming behaviors

UR1268 Biopolymeres Interactions Assemblages, INRA, F-44300 Nantes Cedex 3, France.
Langmuir (Impact Factor: 4.19). 11/2008; DOI: 10.1021/la802357m
Source: OAI

ABSTRACT The binding of a cationic surfactant (hexadecyltrimethylammonium bromide, CTAB) to a negatively charged natural polysaccharide (pectin) at air-solution interfaces, was investigated on single interfaces and in foams, versus the linear charge densities of the polysaccharide. Beside classical methods to investigate polymer/surfactant systems, we applied, for the first time concerning these systems, the analogy between the small angle neutron scattering by foams and the neutron reflectivity of films to measure in situ film thicknesses of foams. CTAB/pectin foam films are much thicker than that of the pure surfactant foam film but similar for highly and lowly charged pectin/CTAB systems despite the difference in structure of complexes at interfaces. The improvement of the foam properties of CTAB bound to pectin is shown to be directly related to the formation of pectin-CTAB complexes at the air-water interface. However, in opposition to surface activity, there is no specific behavior for the highly charged pectin: foam properties depend mainly upon the bulk charge concentration, while the interfacial behavior is mainly governed by the charge density of pectin. For the highly charged pectin, specific cooperative effects between neighboring charged sites along the chain are thought to be involved in the higher surface activity of pectin/CTAB complexes. A more general behavior can be obtained at lower charge density either by using a lowly charged pectin or by neutralizing the highly charged pectin in decreasing pH. .

0 Bookmarks
 · 
65 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Zeolite beta (Si/Al∼18) was synthesized from a single template reaction mixture in a one-step hydrothermal treatment. By adjusting the synthesis conditions, the formation of isolated nanocrystals or mesoporous aggregates of zeolite beta was achieved. Depending on the synthesis conditions, zeolite beta nanocrystals of approximately 20–150nm in diameter or mesoporous aggregates of approximately 120–140nm in diameter were prepared. The use of concentrated synthesis gels resulted in mesoporous aggregates of nanocrystals and diluted reaction mixtures resulted in isolated zeolite nanoparticles. The crystallinity of the samples determined from pXRD patterns is similar to that of commercially available micron-sized zeolite beta. The samples had surface areas of greater than 600m2/g and mesopore volumes of 0.4–0.5cc/g.
    Microporous and Mesoporous Materials - MICROPOROUS MESOPOROUS MAT. 01/2011; 143(1):97-103.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Emulsions are widely used in pharmaceutics for the encapsulation, solubilization, entrapment, and controlled delivery of active ingredients. In order to answer the increasing demand for clean label excipients, natural polymers can replace the potentially irritative synthetic surfactants used in emulsion formulation. Indeed, biopolymers are currently used in the food industry to stabilize emulsions, and they appear as promising candidates in the pharmaceutical field too. All proteins and some polysaccharides are able to adsorb at a globule surface, thus decreasing the interfacial tension and enhancing the interfacial elasticity. However, most polysaccharides stabilize emulsions simply by increasing the viscosity of the continuous phase. Proteins and polysaccharides may also be associated either through covalent bonding or electrostatic interactions. The combination of the properties of these biopolymers under appropriate conditions leads to increased emulsion stability. Alternative layers of oppositely charged biopolymers can also be formed around the globules to obtain multi-layered "membranes". These layers can provide electrostatic and steric stabilization thus improving thermal stability and resistance to external treatment. The novel biopolymer-stabilized emulsions have a great potential in the pharmaceutical field for encapsulation, controlled digestion, and targeted release although several challenging issues such as storage and bacteriological concerns still need to be addressed.
    International Journal of Pharmaceutics 06/2012; 436(1-2):359-78. · 3.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Foamed products are a popular class of food products. The mechanism of stabilization of the air bubbles is often only partially understood. The current study aims at better understanding the stabilization of air-water interfaces through the low molecular weight surfactant polyglycerol ester (PGE). We chose PGE films as an exemplary case for a non-equilibrium situation at an air-water interface--a situation that requires the development of new experimental techniques. Several different film preparation and transfer methods onto solid substrates have been tested. The films were then investigated by scanning force microscopy, and structural artifacts associated to the sample preparation were identified and discussed. In addition to the study of Langmuir monolayers and Gibbs adsorption layers, we have proposed a new approach to investigate the skins of foam bubbles. We thereby were able to determine that PGE indeed covers bubbles by a multilayer structure and that the pH plays a role in the structuring of the films. We show that a combination of different film preparation methods allows us to get an insight into the aggregation behavior of PGE at the air-water interface and thereby better understand the stabilization mechanism of this particular surfactant.
    Journal of Colloid and Interface Science 01/2012; 374(1):164-75. · 3.17 Impact Factor

Full-text

View
0 Downloads
Available from