A Small-Angle Neutron Scattering Study of the Structure of Gelatin/Polyelectrolyte Complexes

Abstract

Mixtures of a fractionated gelatin with very low concentrations of anionic polyelectrolytes have been studied by small-angle neutron scattering. The scattering pattern observed from the system is reminiscent of that from pure polyelectrolyte solutions, with a maximum in the scattering, but at a much greater intensity. The position of the scattering peak is independent of the polyelectrolyte molecular weight, but moves to larger momentum transfer, Q, with increasing concentration. The scattering intensity at higher Q reflects the extent of complexation of the gelatin and polyanion. The addition of salt removes the peak from the scattering pattern and high salt concentrations weaken the complexes. Raising the pH also weakens the complexes. At high pH (g10), the scattering indicates that there is no interaction between gelatin and the polyanions. The extent of complex formation for similar polyelectrolytes depends on the charge density and distribution in the chain.

A small-angle neutron scattering study of poly(ethylene oxide) microstructure in aqueous poly(styrenesulfonate sodium) solutions

“…2), suggesting a structural change of d-PEO in solution: one evidence is the obvious increase in scattering intensity at low-Q, normally associated with large scale structure formations, presumably dilute aggregates of d-PEO in our case [18]; another evidence is that with the increase in PSSNa concentration (at 3 mg mL À1 ), a weak peak gradually becomes evident (around Q = 0.016 Å À1 ), which normally is found in SANS spectra for polyelectrolyte in salt free solutions. This suggests that d-PEO is in some degree structured by PSSNa, even though PSSNa has been made invisible in this study with PSSNa contrast matched [19]. The fact that the maximum is so weak compared to PSSNa or PSSNa-gelatin (strong interacting system [19]) solutions again indicates that the interactions between PSSNa and d-PEO are negligible.…”

“…This suggests that d-PEO is in some degree structured by PSSNa, even though PSSNa has been made invisible in this study with PSSNa contrast matched [19]. The fact that the maximum is so weak compared to PSSNa or PSSNa-gelatin (strong interacting system [19]) solutions again indicates that the interactions between PSSNa and d-PEO are negligible. Fig.…”

“…It is interesting to compare the position of this scattering peak (Q Ã ), i.e., in PSSNa solutions, this peak position is only dependent on polyelectrolyte concentration and salt concentration, but independent from polyelectrolyte molecular weight. A relationship of Q Ã = 0.0117c 1/2 was found, where Q Ã is in the unit of Å À1 and c is the PSSNa concentration in the unit of mg mL À1 ; the PSSNa-gelatin complexes also can fit into this equation [19]. Therefore, if, in our study, PEO and PSSNa forms complexes, a peak position of Q Ã = 0.020 Å À1 (for c = 3 mg mL À1 ) is expected, which is higher than our observation (Q Ã = 0.016 Å À1 ), thus representing a shorter correlation length.…”

“…This peak is regarded as a correlation hole [21,22], which, according to de Gennes, is a virtual tube surrounding the charged chains where other chains are excluded, thus representing the average separation between chains [23]. The correlation between d-PEO chains is rather weak according to the intensity of this peak, in contrast to the strong scattering peak in the mixtures of gelatin and PSSNa, where complexes were formed due to strong interactions between them [19]. It is interesting to compare the position of this scattering peak (Q Ã ), i.e., in PSSNa solutions, this peak position is only dependent on polyelectrolyte concentration and salt concentration, but independent from polyelectrolyte molecular weight.…”

Immobilized Gelatin–λ–Carrageenan on Magnetite Nanoparticles as an Efficient Organocatalyst for Enantioselective Biginelli Reaction

“…Moreover, the produced polymer complex is a kind of Polyelectrolyte complex (PEC), which will be formed by the electrostatic attraction of two oppositely charged polyelectrolytes (Carrageenans as negative part and gelatin as positive part) when mixed in the aqueous solution . Previously, the electrostatic interaction has been suggested as Previously, the electrostatic interaction has been suggested as the main driving force for the formation of complexes main driving force for the formation of complexes between positively charged gelatin and negatively charged polyanions e. g. sodium poly(styrene sulfate) or sodium poly(2–acrylamido–2–methylpropanesulfonate) …”