Dilational rheology and relaxation properties of the adsorption layers of electrostatic complexes between Eudragit RS and chitosan sulfate at the methylene chloride-water interface.

International audienceThe electrostatic interpolyelectrolyte complex formation between the hydrophobic cationic polyelectrolyte Eudragit RS and the anionic hydrophilic polyelectrolyte chitosan sulfate at the methylene chloride–water interface has been studied by dilational rheometry

Dilational viscoelasticity and relaxation properties of interfacial electrostatic complexes between oppositely charged hydrophobic and hydrophilic polyelectrolytes

Strongly adsorbing hydrophobic cationic polyelectrolyte, Eudragit RS, containing approximately 2.5 mol% of pendent hydrophilic trimethylammonium (TMA) groups irreversibly adsorbs from its methylene chloride (MCl) solution at the MCl/water interface and forms solid-like adsorption layers (ALs). Submitted to periodic dilational deformations with the standard radial frequency omega(0)=0.63 rad/s, these ALs exhibit relatively high dilational storage modulus E\u27 approximately 20 mN/m and practically zero loss modulus E\u27\u27 at the bulk concentration C(Eud)=4 x 10(-3)g/L. The frequency scanning of these ALs in the diapason omega=0.01-0.63rad/s and the approximation of the experimental dependences E\u27(omega) and E\u27\u27(omega) by two relaxation times rheological model makes it possible to estimate the crossing frequency of these ALs determined from the condition E\u27(omega(c))=E\u27\u27(omega(c)) as omega(c) approximately 5 x 10(-4)rad/s. Upon dissolving the hydrophilic anionic polyelectrolyte, chitosan sulfate (ChS), in the water phase (C(ChS)=3 x 10(-2)g/L) the electrostatic interpolyelectrolyte complexes form at the MCl/water interface. The elasticity moduli E\u27 and E\u27\u27 of these mixed AL did not undergo remarkable variations, but the crossing frequency is sharply increased by approximately 10 times becoming equal to omega(c) congruent with 3 x 10(-3)rad/s. The increase of omega(c) certifies for the liquefaction of mixed Eudragit RS/ChS adsorption layers. A remarkable decrease of the storage modulus down to E\u27=8 mN/m and simultaneous increase of the crossing frequency up to omega(c) congruent with 10(-2)rad/s occurs upon increasing the concentrations of both components, Eudragit RS and ChS, up to 0.1g/L. The liquefaction effect in the mixed ALs of oppositely charged polyelectrolytes was explained on the basis of the proposed relaxation mechanism. The effect of the liquefaction of adsorption layers of strongly adsorbing hydrophobic polyelectrolytes by formation of interpolyelectrolyte complexes with hydrophilic polyelectrolytes must be taken into account in the production of nano-capsules and nano-fibers

Dilational viscoelasticity of the adsorption layers of hydrophobically modified chitosans

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Interfacial properties of amphiphilic natural polymer systems based on derivatives of chitin

cited By 13International audienceThis short review highlights characterizations of amphiphilic polysaccharide systems based on chitin derivatives. Two routes are detailed: grafting hydrophobic moieties onto the macromolecular backbone and the addition of an oppositely charged surfactant to form an electrostatic complex. Attention to the surface tension, kinetics of adsorption, and formation of a structural adsorption layer is used to inform a comparison of the various interfacial properties of these systems. © 2006 Society of Chemical Industry

Dynamic surface tension of hydrophobically modified chitosans

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Interfacial properties of amphiphilic systems on the basis of natural polymers-chitin derivatives

cited By 5International audienceA review of the amphiphilic derivatives of chitin, obtained by covalent grafting of hydrophilic and hydrophobic radicals, is given. It is shown that water-soluble alkylated derivatives of chitin and chitosan, as well as surfactant-polyelectrolyte complexes between oppositely charged surfactants, exhibit interfacial activity, forming structured (gel-like) adsorption layers (AL). Gel formation inside AL of chitin derivatives is characterized by means of interfacial dilational rheometry. © 2008 MAIK Nauka

Interfacial properties of ionic amphophilic systems based on polysaccharides [Propriétés interfaciales de systèmes amphiphiles ioniques àbase de polysaccharides]

cited By 1International audienceAmphiphilic ionic polysaccharides based systems, and more particularly chitin derivatives based ones, can see their amphiphily modified through covalent grafting of hydrophobic chains or the formation of a complex with an oppositely charged surfactant (called SPEC). This work presents the study of the kinetics of the adsorption and of the formation of a structured layer of amphiphilic derivatives of chitosan and SPECs, by dynamic tensiometry and two-dimensional dilatational rheology. Adsorption steps with different characteristic times are demonstrated. The macromolecules take up an extended conformation at the interface. The interfacial activity and kinetics of adsorption do not depend for a monotonous manner upon the degree of substitution and the length of the grafted alkyl chain but the conformation of macromolecules was also an important parameter. The adsorption layer has a "solid-like" behaviour related with the structuring of this layer. As in static tensiometry surfactant-polyelectrolyte complex appears as more efficient the polysoaps considering the adsorption kinetics

Effect of electrolyte concentration on the dynamic surface tension and dilational viscoelasticity of adsorption layers of chitosan and dodecyl chitosan

International audienc

Dynamic surface tension and dilational viscoelasticity of adsorption layers of a hydrophobically modified chitosan

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