Structure des solutions de polyélectrolytes : apport de la diffusion des rayons X et des neutrons aux petits angles

Combet, J.

doi:10.1051/sfn/201011010

Cited by 2 publications

(4 citation statements)

References 30 publications

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“…This feature has already been observed in polyelectrolyte solutions and is attributed to differences in the intramolecular interactions that can be seen between SAXS and SANS due to the different contrasts . In small-angle scattering, the scattered intensity I ( q ) by polyelectrolytes is composed of both the signal of the chains and the signal of the counterions as follows: where S mm ( q ), S cc ( q ) and S cm ( q ) are, respectively, the monomer/monomer, counterion/counterion, and counterion/monomer partial scattering functions. , Table gives the contrast values of the modified ionene monomer (Δρ) 6im 2 , the (Δρ) X (Δρ) 6im values, and the contrast values of the different counterions (Δρ) X 2 in heavy water (for SANS) and in light water (for SAXS). The respective contributions of the different partial scattering functions are weighted by the contrasts of the monomers and the counterions.…”

Section: Resultsmentioning

confidence: 82%

“…The mesh size of the gel Ξ is located at similar q values in SAXS and SANS curves, whereas the correlation length ξ is located at lower q values by SAXS compared to SANS. This feature has already been observed in polyelectrolyte solutions and is attributed to differences in the intramolecular interactions that can be seen between SAXS and SANS due to the different contrasts . In small-angle scattering, the scattered intensity I ( q ) by polyelectrolytes is composed of both the signal of the chains and the signal of the counterions as follows: I ( q ) = false( normalΔ ρ false) normalm 2 S mm ( q ) + false( normalΔ ρ false) normalc 2 S cc ( q ) + 2 false( normalΔ ρ false) normalm false( normalΔ ρ false) normalc S c m ( q ) where S mm ( q ), S cc ( q ) and S cm ( q ) are, respectively, the monomer/monomer, counterion/counterion, and counterion/monomer partial scattering functions. , Table gives the contrast values of the modified ionene monomer (Δρ) 6im 2 , the (Δρ) X (Δρ) 6im values, and the contrast values of the different counterions (Δρ) X 2 in heavy water (for SANS) and in light water (for SAXS).…”

Section: Resultsmentioning

confidence: 82%

Section: Counterion Effects On the Macroscopic Propertiesmentioning

confidence: 99%

“…where S (q), S cc (q) and S cm (q) are, respectively, the monomer/monomer, counterion/counterion, and counterion/monomer partial scattering functions. 37,47 Table 1 gives the contrast values of the modified ionene monomer (Δρ) 6im 2 , the (Δρ) X (Δρ) 6im values, and the contrast values of the different counterions (Δρ) X 2 in heavy water (for SANS) and in light water (for SAXS). The respective contributions of the different partial scattering functions are weighted by the contrasts of the monomers and the counterions.…”

Section: Counterion Effects On the Macroscopic Propertiesmentioning

confidence: 99%

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Tuning Structure and Rheological Properties of Polyelectrolyte-Based Hydrogels through Counterion-Specific Effects

et al. 2023

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Tuning at will the properties of gel-forming systems is of key relevance for many biotechnological, agricultural, and biomedical applications. For polyelectrolyte-based gels, ion-specific effects can be an attractive way for this purpose. This study investigates the counterion-specific effect on the microscopic structure and the rheological properties of a physical hydrogel formed of ionene-type cationic polyelectrolytes. The focus is on two monovalent halide counterions (F– and Cl–) and a divalent counterion (SO4 2–). A strong counterion-specific effect appears within ionene-based gels. In the case of halide counterions, gelation is more effective for more weakly hydrated counterions. Indeed, strongly hydrated counterions maintain electrostatic repulsions between the chains and as a consequence gel formation is shifted toward higher concentrations (higher critical gelation concentration, CGC). The combination of the complementary small-angle X-ray and neutron scattering (SAXS and SANS) techniques reveals a strong contribution of ion–ion correlations in the structure of the gel network. Contrary to chloride gels, which present a single correlation length characterizing the distance between the cross-linking nodes, fluoride gels present an additional network of nodes. This is accompanied by a very rapid increase of the elastic modulus of fluoride gels, once CGC is reached. With divalent counterions, the gelation is even more remarkable with a lower CGC and a higher elastic modulus at equivalent polyelectrolyte concentrations. The presence of divalent counterions favors the association of chains, probably by a bridging effect. This evokes the “egg-box” model, and the characteristic scaling of the elastic modulus with reduced gel concentration confirms this. However, only a narrow concentration window for gel-forming exists for divalent counterions before precipitation takes over due to too strong attractive chain–chain interactions.

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Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 82%

Section: Counterion Effects On the Macroscopic Propertiesmentioning

confidence: 99%

Section: Counterion Effects On the Macroscopic Propertiesmentioning

confidence: 99%

See 2 more Smart Citations

Tuning Structure and Rheological Properties of Polyelectrolyte-Based Hydrogels through Counterion-Specific Effects

et al. 2023

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Small angle neutron scattering

Cousin

2015

EPJ Web of Conferences

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Abstract. Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ∼ 1 nm up to ∼ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ∼ 1 cm 3 . This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area. . . ) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2 nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer configurations, optimization of sample characteristics prior to measurements (thickness, volume, hydrogen content. . . ), standards measurements to be made and principle of data reduction.Résumé. (La Diffusion de Neutrons aux petits angles (DNPA) est une technique permettant de sonder la structure 3-D de matériaux sur une gamme typique de taille comprise entre ∼1 nm) et ∼ quelques 100 nm, les informations obtenues étant statistiquement moyennées sur la taille de l'échantillon dont le volume est d'environ 1 cm 3 . C'est une technique très puissante car elle permet de faire une caractérisation complète de la structure d'un objet donné de dimensions nanométriques (rayon de giration, forme, volume, masse, dimension fractale, surface spécifique. . . ) grâce à la détermination du facteur de forme, ainsi que la détermination de la manière dont les objets sont organisés au sein d'un milieu continu, et donc de décrire les interactions entre les objets, par la détermination du facteur de structure. Les propriétés spécifiques de neutrons (possibilité de modul...

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Structure des solutions de polyélectrolytes : apport de la diffusion des rayons X et des neutrons aux petits angles

Cited by 2 publications

References 30 publications

Tuning Structure and Rheological Properties of Polyelectrolyte-Based Hydrogels through Counterion-Specific Effects

Tuning Structure and Rheological Properties of Polyelectrolyte-Based Hydrogels through Counterion-Specific Effects

Small angle neutron scattering

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